F220
Eye Diseases and Problems

basic anatomy and terms | nasolacrimal duct system | keratoconjunctivitis sicca (kcs) | globe or eyeball | entropion | ectropion | cherry eye | tumors of the eyelid | conjunctivitis | keratitis | ulcerative keratitis | pannus | corneal dystrophy | lenticular sclerosis | cataract | luxation and subluxation of the lens | anterior uveitis | degeneration of the retina | detatchment of the retina | cancers | eye medications

Introduction: It is important to examine dogs’ eyes on a routine basis. Repeated examination allows one to become familiar with the normal appearance of the eye, so any abnormalities will be noticed immediately. Signs of an eye problem vary tremendously and may include cloudiness, tearing, squinting, discharge, redness, blinking, swelling, an increase in blood vessels, or changes in the size or shape of the pupil. Dogs may paw at the eye or rub it in an attempt to relieve irritation and itching. Any change in the eye or surrounding tissue may signal a problem and should be a cause for concern.

Many different problems can result in the same set of disease signs, so diagnosis cannot be made by clinical signs alone. Physical examination and special tests are needed to properly identify the cause of the problem. Tests may include a fluorescein dye test, a test for tear production called a Schirmer test, tests to measure pressure within the eyeball, and ocular examination with different types of lenses. The eye may be dilated to allow for proper visualization of the back of the eye.

Eye problems should be brought to the attention of a veterinarian immediately. Prompt diagnosis and treatment can prevent further eye problems that can lead to loss of sight. In addition, changes in the eyes may be a sign of whole body disease. By immediately identifying and reporting any changes, diseases can be diagnosed early and treatment can begin.

Although all eye problems should be reported to a veterinarian, it is important for the dog owner to identify and recognize common eye ailments. The eye is composed of several parts, all of which can be injured or become diseased. Eye problems and diseases can affect one portion of the eye or simultaneously be found in several areas.

Basic Anatomy and Terms: The eye is protected by upper and lower lids, as well as a third eyelid, called the nictitating membrane. Glands which produce tears are located under the lids. The front portion of the eye itself is covered with a thin, clear covering called the cornea. The remainder of the eye is covered with dense white tissue, the sclera. The margin of the cornea and the sclera is called the limbus. The episclera is the outside surface of the sclera. The conjunctiva is the tissue which reflects from the inside of the eyelids onto the globe. Glands which produce tears are also located in the conjunctiva.

The iris is the colored portion of the eye; the black open space in the iris is the pupil. Behind the pupil is the lens. The lens is attached to the ciliary body. The back of the eye is covered with a layer of tissue called the retina. The inside of the globe is filled with a clear fluid called aqueous humor. This fluid is produced by the ciliary body and nourishes the eye while helping to maintain its shape. This fluid is continually produced and drained from the eye. Drainage occurs at the iridocorneal angle, also called the drainage or filtration angle.

1. Anterior chamber - The space in the eye bounded in front by the cornea and behind by the iris. It is filled with aqueous humor.
2. Anterior uvea - The front portion of the uvea, made up of the iris and ciliary body.
3. Anterior uveitis - Inflammation of the iris and ciliary body.
4. Anti-inflammatory - A medication that reduces inflammation.
5. Aqueous humor - The clear, watery fluid which fills the eye.
6. Blepharitis - Inflammation of the eyelids.
7. Blepharospasm - Spasm of the muscles that control the eyelids.
8. Cataract - An opacity of the lens or its capsule, or both.
9. Choroid - The part of the vascular layer of the eye (uvea) located at the back of the eye. It helps to nourish the retina. It is the posterior uvea.
10. Ciliary body - The part of the vascular layer of the eye (uvea) located between the iris and the choroid.
11. Conjunctiva - The mucous membrane lining the back of the eyelids and the front of the eye, except for the cornea.
12. Conjunctivitis - Inflammation of the conjunctiva.
13. Cornea - The transparent portion of the outer layer of the eye, which allows light to enter the eye. It attaches to the sclera.
14. Corneal pigmentation - The deposition of pigment in the cornea, usually as a response to chronic irritation.
15. Corneal ulceration - An open lesion or sore on the surface of the cornea.
16. Dry eye - See keratoconjunctivitis sicca.
17. Enucleation - Removal of the eye.
18. Epiphora - The abnormal flow of tears over the face.
19. Fibrous - Composed of cells that form tough, connective tissue.
20. Fluorescein dye - A special dye that is applied to the cornea that will outline ulcerations in the cornea. The dye will not penetrate intact cornea or conjunctiva, but will adhere to and outline areas of ulceration.
21. Glaucoma - Increased ocular pressure resulting from altered flow of aqueous humor.
22. Globe - The eyeball.
23. Intraocular - Within the eyeball.
24. Iris - The colored, circular portion of the eye located behind the cornea. It is part of the uvea.
25. Keratoplasty - Corneal grafting used as a repair technique.
26. Keratectomy - Removal of part of the superficial layers of the cornea.
27. Keratitis - Inflammation of the cornea.
28. Keratoconjunctivitis sicca (KCS) - A condition of the eye caused by lack of proper tear production that results in inflammation of the cornea and conjunctiva. Also called dry eye.
29. Lacrimal apparatus - The structures in the eye responsible for tear production.
30. Lenticular sclerosis - A gradual hardening and thickening of the lens that accompanies aging. This does not interfere with vision.
31. Lens - A transparent structure suspended in the front portion of the eye. It refracts light that passes through the cornea on its way to the retina.
32. Lens luxation - Displacement of the lens.
33. Miosis - Contraction of the pupil so that the pupil becomes small.
34. Miotic - A medication that causes the pupil to become small.
35. Mucoid - This is a general term for types of secretions that are made up of mucous materials.
36. Mucopurulent - A secretion or exudate that is made up of pus and mucous.
37. Mydriatic - A medication that causes the pupil to become large.
38. Mydriasis - A dilated pupil.
39. Nasolacrimal - The system of the eye responsible for proper drainage of tears out of the eye and into the inside of the nose.
40. Nictitans (nictitating membrane) - The third eyelid.
41. Ophthalmoscope - A device for studying the interior of the eyeball.
42. Optic nerve - The nerve that originates from the retina and carries light signals to the brain.
43. Pannus - A type of keratitis characterized by vascularization and scarring of the cornea, accompanied by deposits of pigment.
44. Pigmentation - Any abnormal coloration of an area.
45. Posterior uvea - The portion of the uvea made up of the choroid.
46. Posterior uveitis - Inflammation of the choroid.
47. Pupil - The circular opening in the center of the iris through which light passes into the eye.
48. Primary - The first, or foremost. Used in this case to describe problems that occur first and may be followed by other, secondary problems.
49. Progressive Retinal Atrophy (PRA) - A degeneration of the retina, which ultimately leads to blindness.
50. Proptosis - Prolapse of the eye.
51. Retina - The innermost coat of the eye, formed of cells sensitive to light.
52. Retinal degeneration - A progressive, pathological change that interferes with the function of the retina.
53. Retinal detachment - Separation of the retina from the underlying tissue, the choroid.
54. Schirmer tear test - A method of measuring tear production using small strips of absorbent paper placed into the lower corner of the eye.
55. Sclera - This is a layer of dense connective tissue that supports the eye. It is the white portion of the eye that connects to the cornea. The cornea and sclera make up the fibrous tunic of the eye.
56. Secondary - A problem or disease which occurs after the first or primary disease or problem.
57. Tonometry - The measurement of intraocular pressure.
58. Topical - Medication that is applied locally on an external portion of the eye.
59. Uvea - The portion of the eye which contains many blood vessels. It is comprised of the iris, ciliary body, and choroid. It is called the vascular tunic.
60. Uveitis - Inflammation of the uvea.
61. Vascular - Containing blood vessels.
62. Vascularization - The formation of new blood vessels in a part of the body.

Copyrighted graphic used by permission from Anatomy of Domestic Animals, Sudz Publishing (email: sudzpub@mac.com)

If there is a problem with any part of the system, drainage of tears from the eye may be impeded. If the tears do not drain into the duct system, they will spill over onto the face, creating a condition called epiphora. Signs include wet facial skin and a reddish, rusty stain to the skin and hair near the inner corners of the eyes.

1. Absence of the Puncta: There can be many different causes for obstructions in the nasolacrimal duct system. Blockage will occur if the openings to the ducts, called the puncta, are absent or closed. Dogs may be born with closed or absent puncta. This condition occurs in many breeds, including poodles, cocker spaniels, golden retrievers, and some terriers. Diagnosis is based on physical examination and specialized tests. Tests may include the use of fluorescein dye to observe the movement of tears, a nasolacrimal flush, and passage of a nasolacrimal catheter. If a potentially functional duct system exists, treatment involves opening the puncta with surgery. Once the duct is created or opened, a catheter can be placed for one to two weeks to ensure it remains open. The eye is also treated simultaneously with topical medication to reduce inflammation and prevent infection.
    
2. Obstruction of the Puncta or Ducts: Other causes of obstructions may include inflammation that closes down any part of the duct system. This obstruction can be caused by conjunctivitis or by physical irritants such as sand, plant stems, and other foreign objects. Diagnosis is based on ocular examination and appropriate testing. Treatment would include antibiotic and anti-inflammatory medical therapy, removal of any foreign objects, and flushing of the duct system. Additional causes of obstruction may include space-occupying tumors. Treatment would depend upon the type and location of the tumor and may include surgical removal.
    
3. Epiphora: Miniature breeds, including small terriers, small poodles, and the Maltese, have facial anatomy that predisposes them to tear drainage down the front of the face. Many owners of small breed dogs are concerned to find that the dogs demonstrate epiphora (clear tear drainage visible on the face) with rust-colored staining of the skin and hair. These dogs may have one or more of several conditions contributing to improper drainage of tears. These conditions can include the hair near the eyes acting as a wick to pull the tears onto the face, absence of the nasolacrimal puncta, obstruction of any part of the nasolacrimal duct system, excessive tear production caused by irritation or infection, inverted lower eyelids (entropion), or a prominent eye with a very small area for tears to pool. Typically, tears pool together in the inner corner of the eye before entering the duct system. Any dog with a flattened face and large, prominent eyes has a diminished area for the tears to pool, resulting in spillage over the lower lid.
   
   Diagnosis is based on physical examination and testing. Treatment may include surgery to correct underlying anatomical abnormalities, topical medications such as antibiotics, oral medications, and daily cleaning of the face and hair. Many dogs respond favorably to treatment with oral antibiotics, but the epiphora returns when the medication is stopped. Medical control requires long term continuous or intermittent treatment.
   
   Prognosis depends on the cause of the epiphora and elected treatment protocol. If the condition is not associated with any other ocular problems, or is causing corneal and/or conjunctival irritation, it may be considered a cosmetic issue and controlled with daily cleaning of the affected area.
   
   

Introduction: Tears are produced by the lacrimal glands, the accessory lacrimal glands, and the gland of the third eyelid. The tear film is actually three different layers - mucin (protein), serous (water), and lipid (fat). These different components of the tear film are made by different glands in the eye. Problems related to the lacrimal system cause a reduction in tear production and/or a change in the composition of the tear film. A decrease in tear production can be caused by injury or removal of the tear-producing glands, destruction of the glands, or infections. Inadequate tear production can lead to severe irritation of the cornea and surrounding structures. In addition, inflammation, infection, or destruction of one type of tear gland may result in alteration of the composition of the tear film and cause disease even if it appears that adequate amounts of moisture are being produced.

1. Keratoconjunctivitis Sicca (KCS) is the most common disease caused by a reduction in tear production in dogs. Often called "dry eye," the condition is characterized by a significant decrease in the tears and a change in the composition of those tears that are produced. This allows drying out and inflammation of the cornea and conjunctiva. The condition is believed to have an immunological basis in that these dogs produce antibodies to their own lacrimal glands, thereby destroying them. Other possible causes for KCS include chronic conjunctivitis, chronic eyelid and conjunctival inflammation, untreated chronic endocrine disease such as hypothyroidism, drug toxicity, distemper infection, removal of the gland of the third eyelid, and trauma.
   
   All dogs can suffer from this condition; however, some of the breeds considered at risk for the disease include cocker spaniels, cavalier King Charles spaniels, English bulldogs, Lhasa apsos, shih tzus, pugs, shar-peis, West Highland white terriers, miniature dachshunds, miniature schnauzers, Yorkshire terriers, and bloodhounds. Any age dog may be affected. The signs of KCS can include ocular discharge, reddening of the eye, swelling of the conjunctiva, squinting, spasm of the lids, eye pain, and avoidance of the sun. Visible changes to the cornea include pigmentation, ulceration, cloudiness, scar formation, and vascularization. The ocular discharge is typically mucopurulent or mucoid, not clear. Heavy mucus may accumulate in the eye. In some dogs, the third eyelid is more prominent than usual. Chronic, untreated cases can result in loss of vision.
    

   Figure #2: This picture shows a dog with keratoconjunctivitis sicca (KCS). Notice the heavy mucus discharge around the edges of the eye.

   Diagnosis is based on visual examination and the use of a Schirmer tear test. This test demonstrates the reduction or lack of tear production. Fluorescein staining may show cornea irritation, abrasion, or ulceration. Blood tests may confirm the presence of autoimmune disease.
   
   Treatment involves restoration of the tear film and treatment of secondary infections and inflammation. The eye must be cleaned before any medications are administered to ensure the efficacy of the medications. This can be done with sterile saline eye washes or tear solutions. Conservative therapy involves the use of artificial tears and lubricants administered several times per day, topical antibiotics, topical corticosteroids to treat inflammation, and if indicated, drops that break up mucus. Primary therapy involves increasing tear production by reducing the immune system’s destruction of the lacrimal glands. This is accomplished using a topical medication called cyclosporine. Approximately 75% of dogs respond to treatment with cyclosporine by increasing tear production. Other therapies that increase tear production include pilocarpine, and if needed, surgery to transplant the parotid salivary duct into the corner of the eye. Additional surgery may be needed to treat corneal ulceration if it is present.
   
   Prognosis depends on the length of time between the onset of disease and treatment, as well as the individual’s response to treatment with cyclosporine. Treatment should be instituted as early in the course of the disease as possible. If treatment is delayed, vision-impairing corneal changes can occur. Most dogs respond to treatment with cyclosporine, so surgical therapy can be avoided. Topical treatment may need to be continued for the life of the pet.
   
   
   

1. Proptosis of the Eyeball: Proptosis literally means "falling forward." In this case, the eyeball pops out if the socket. This condition typically occurs following facial trauma, such as an automobile accident or a dog fight. Breeds of dogs with flat faces, such as the Pekingese or the pug, are prone to this occurrence. Because of their facial anatomy, minor trauma can result in the eyeball popping out of the socket. The problem can, however, occur in any animal if the trauma is great enough. In rare cases, a tumor behind the eyeball causes it to be pushed out of the socket.
   
   This condition is easily identified because the globe is out of the socket and pushed in front of the eyelids. This results in swelling, cloudiness, eyelid entrapment, and inflammation of all associated structures. Other accompanying signs may include an ulcerated or dried out (desiccated) cornea, abnormal pupil size, hemorrhage of the eye or in the conjunctiva, and rupture of the globe. If the optic nerve is cut or compressed, blindness may result. Depending on the cause, other signs of facial trauma, such as fractures, bruising, and bleeding, may be evident. The animal may also be in shock or have other signs of trauma to the face or body.
   
   To prevent blindness, emergency treatment should be started as rapidly as possible. The cornea should be lubricated immediately to prevent further damage. The animal must be assessed, and shock and other traumatic damage treated as necessary. If the patient is stable, the globe should be returned to its socket surgically. This is most easily done under sedation or anesthesia. This is followed by medical treatment to reduce swelling and prevent or treat infection. The globe cannot be repositioned if it is severely damaged, infected, or desiccated, or if the optic nerve is severed; these eyes are usually removed. Follow-up treatment involves both whole body (systemic) and topical medication with antibiotics and corticosteroids as indicated by the condition of the eye and the patient.
   
   Prognosis depends on the time from onset until treatment, along with the amount of damage to the eye and surrounding structures. Potential outcomes include a permanently dilated pupil, decreased tear production, desiccation of the cornea, and turning of the eye to a position in the upper, outer corner of the eye (dorsolateral strabismus). Some dogs will improve over time, others will not. Most eyes can be saved, however, some may need to be removed. Many dogs will not regain sight. Permanent blindness can result if the optic nerve is injured, treatment is delayed, or there is too much damage or swelling to replace the globe. Removal of the globe may be necessary if pain or damage to the eye is present.
    
2. Glaucoma: Glaucoma is one of the most common and serious eye diseases of dogs. It is defined as an abnormal increase in pressure inside the eyeball (intraocular). It is caused by impairment to the drainage of aqueous humor. Aqueous humor, the fluid that nourishes the eye, is continually produced and drained from the eye. It is drained at an area called the iridocorneal angle. This area is bounded in the front at the location where the cornea meets the sclera and behind at the location where the lens meets the musculature of the ciliary body. If this area is blocked, drainage is impeded. If drainage is impeded, fluid and pressure build in the eye, damaging internal structures. Damage to the retina and optic nerve can result in permanent loss of vision.
   
   Glaucoma can either exist as the primary problem, or it may be secondary to other diseases, such as luxation of the lens, uveitis, neoplasia, or bleeding in the eye. The condition may be acute or chronic. Primary glaucoma can be an inherited disease. Breeds at risk for primary glaucoma include cocker spaniels, beagles, Norwegian Elkhounds, Siberian huskies, basset hounds, Samoyeds, and chow chows. Breeds at risk of glaucoma secondary to lens luxations include terriers such as Boston terriers, West Highland white terriers, cairn terriers, Norfolk terriers, Norwich terriers, and many others.

   Acute glaucoma has a rapid onset. The rapid increase in intraocular pressure results in an extremely painful eye. The pain can cause eyelid spasm and epiphora. The dog may resist examination, refuse to eat, be depressed, and even cry out from the pain. In addition, ocular discharge, redness, and cloudiness may be noticed. 

   Figure #3: This eye shows the typical signs of glaucoma: cloudiness, corneal edema, redness, and engorgement of the blood vessels in the episclera.

   Diagnosis is based upon examination of the eye and measurement of the pressure in the globe. Upon examination, the glaucomatous eye may have cloudiness, corneal edema, redness, and engorgement of the blood vessels in the episclera. The pupil may be dilated and unmovable. The globe may be enlarged and firm to the touch. Accompanying problems such as uveitis, a luxated lens, or neoplasia may be noted. Specific eye examination may show a closure of the normal drainage area of the eye. The blood vessels in the retina may be compressed by the increase in pressure. Measurement of the intraocular pressure will show it to be elevated. Definitive diagnosis is based on measurement of an elevated intraocular pressure. Acute glaucoma can very rapidly lead to blindness. Total, irreversible blindness can occur in as little as 24-48 hours.
   
   Treatment of acute glaucoma is considered an emergency. Rapid treatment may prevent permanent blindness. If the glaucoma is secondary to an underlying cause, treatment of the primary cause may result in resolution of the glaucoma. Medical treatment is initially used for treatment of primary glaucoma. Medical treatment may include diuretics, such as mannitol, and topical medications to reduce aqueous production. Drugs can be applied directly to the eye to reduce aqueous humor production, including carbonic anhydrase inhibitors such as dichlorphenamide, and B-adrenergic antagonists such as timolol maleate. Other drugs that help to open drainage and enhance the outflow of aqueous humor may be tried. These include pilocarpine and demecarium bromide.
   
   If medications are insufficient to lower the intraocular pressure, surgical treatment is needed. Surgery may be done to reduce the production of aqueous humor and to create drainage. Laser treatment may be used. A combination of medical and surgical therapies may be needed for long-term control of the problem. It is important to note that if only one eye is involved, both eyes should be medicated. If treatment is not successful and blindness results, removal of the eye may be recommended to eliminate the pain associated with the condition. If complete eye removal (enucleation) is unacceptable, the contents of the eye may be removed (eviscerated) and an insert is placed inside the eye (intraocular prosthesis) to maintain its form.
   
   Chronic glaucoma occurs if the signs of acute glaucoma go unnoticed, or if acute glaucoma therapy is not effective. The signs may include all of those noticed with acute glaucoma, although to a lesser degree. The most obvious sign is the enlarged globe. In addition, corneal ulceration, lens luxation, cataracts, and keratitis may occur. Ocular examination will show degeneration of the retina and the head of the optic nerve. The animal is typically blind in the affected eye. Diagnosis is based on the physical and ocular examination.
   
   Treatment is aimed at reducing the pain of chronic glaucoma. The blindness is not reversible. The medical and surgical treatments described for the control of acute glaucoma may be used. Removal of the eye may be needed to control pain. If only one eye is affected, the normal eye should be examined and monitored for any signs of glaucoma. Preventative (prophylactic) treatment of the unaffected eye should be started if indicated by ocular examination.
   
   Prognosis for treatment of glaucoma depends on the underlying cause and the time between onset of disease and treatment. Treatment to maintain or restore vision will be unsuccessful in acute glaucoma cases unless initiated within hours of onset. Chronic glaucoma patients may be blind before treatment begins. Secondary glaucoma cases can resolve following successful treatment of the primary cause. This can occur with glaucoma secondary to lens luxation.
   
   Primary glaucoma patients require continual therapy to ensure any measure of therapeutic response. Even with prompt medical treatment, over 90% of patients will lose vision within one year of initial diagnosis. With surgical treatment, approximately 60% will still have vision in the affected eye one year later. Approximately 50% of dogs with one diseased eye will have the other eye affected within one year if the second eye does not receive preventative treatment.

Problems with the lids can result in pain, swelling, redness, excessive tearing, and drainage from the eye. Dogs with lid pain may rub their eyes, paw at their faces, squint, and show other signs of pain. Problems with the lids can lead to additional problems with closely associated structures such as the cornea, conjunctiva, and nasolacrimal drainage system of the eye.

1. Entropion: This is a condition of the lids characterized by an inward turning of the lids. The inward turning is called inversion. The turned-in lids can result in irritation and abrasion of the cornea caused by contact with either the eyelid itself or hairs on the eyelid. This can lead to corneal ulceration, which will interfere with vision. Severe, untreated entropion can lead to perforation of the cornea.
   
   The condition can be seen in any dog, but is most often seen in breeds such as the chow-chow and the shar-pei. It is also identified commonly in sporting dogs, giant breeds, toy breeds and brachycephalic breeds (dogs with flat faces). Examples include bloodhounds, Norwegian elkhounds, English springer spaniels, cocker spaniels, Labrador retrievers, golden retrievers, Chesapeake Bay retrievers, mastiffs, Newfoundlands, St. Bernards, Lhasa apsos, pugs, the Pekingese, poodles, Akitas, Rottweilers, and English bulldogs.
   
   Entropion is often identified in young dogs, less than one year of age. In severely affected breeds, the condition may be seen in puppies as young as 2 weeks of age. Signs of entropion will vary with the severity, but may include drainage of clear tears, chronic discharge of infectious material, squinting, pigment changes on the cornea, corneal inflammation and ulceration, and corneal rupture. Causes include facial anatomy which predisposes the dog to an inward rolling of the eyelids, chronic infections, or any trauma or irritant that causes spasm of the eyelids. The majority of dogs with entropion have breed-specific facial anatomy that leads to this problem.
    

   Figure #4: This dog has entropion as shown by the inward turning of the eyelashes on the bottom eyelid.

   Diagnosis is based on physical examination. Treatment involves eye medications such as antibiotics and anti-inflammatory medications to treat underlying causes of squinting and spasm. Temporary sutures may be placed to evert the lid and decrease irritation to the eye. Once underlying causes are treated, those cases that continue to have entropion are treated with surgical techniques to roll the eyelid out and reduce irritation. Puppies are often treated with temporary sutures. Permanent surgery is not performed until the dogs reach full body size at about 6 months of age. If not treated, permanent irritation and scarring of the cornea can result, along with chronic tearing and pain. Prognosis is good with proper therapy and surgery as needed.
    

2. Ectropion: This is a rolling out of the eyelids. The outward turning is called eversion. This results in exposure of the conjunctiva. Exposure of the conjunctiva can result in inflammation and disease of the conjunctiva and cornea. Chronic changes in the cornea caused by ectropion can lead to loss of vision.
   
   This problem can be found in any breed, but there is an anatomical genetic predisposition in breeds such as bloodhounds, basset hounds, black and tan coonhounds, mastiffs, Rottweilers, giant breeds such as St. Bernards, and sporting dogs such as hounds, spaniels, and retrievers. Ectropion problems typically are identified before the dogs reach one year of age. Older onset of ectropion may be secondary to any disease that results in changes to the shape or musculature of the face. This can include injury, hypothyroidism, weight loss, muscle disease, and neurological disease that affects the nerves to the eyelids.
   
   Signs of ectropion include the visible outward rolling of the eyelid with exposure of the conjunctiva. Associated conditions include drainage from the eye, recurrent infections of the eye, and irritation and inflammation of the conjunctiva. Drainage may be mucoid (looks like mucus) or mucopurulent (looks like mucus and pus) and is accompanied by staining of the face. Dogs with a history of ectropion may continually get conjunctivitis, eye irritation, or foreign bodies in their eyes.
   
   Treatment includes applying lubricants and protectants to the eye and conjunctiva and treating infections with appropriate antibiotics. Daily cleaning of the eyes and face are part of this therapy. If conservative therapy does not control the irritation and infection, definitive therapy includes corrective surgery to reduce or lift the eyelid.
   
   Prognosis is good with appropriate therapy. Dogs treated with non-surgical techniques must be monitored for signs of worsening disease or secondary infections.
   
    
3. Distichiasis: This condition is characterized by eyelashes that grow toward the eye instead of away from it, resulting in lashes that can touch and irritate the cornea. The lashes grow from parts of the eye other than the lids, such as openings to specialized glands called the meibomian glands. These openings are found on the lid margin. There is probably a genetic predisposition to the condition and it is most commonly found in certain breeds, such as cocker spaniels and Yorkshire terriers. In addition, bulldogs, the Pekingese, golden retrievers, Lhasa apsos, Labrador retrievers, Siberian huskies, and poodles have a tendency to distichiasis. The condition has also been identified in St. Bernards and Lakeland terriers.
   
   Distichiasis is typically identified in young dogs. Signs may include discharge from the eye, squinting, conjunctivitis, corneal irritation, and corneal inflammation. The irritation to the cornea can result in pigmentation, ulceration, and vascularization. Diagnosis is based on ocular examination. Treatment involves surgical removal of the "wild" or aberrant hairs. Because the hair will grow back, simply pulling out the hair is not curative. Instead, steps must be taken to destroy the hair follicles so that the hairs do not regrow. There are a variety of techniques that can be used. These include surgical removal, cryotherapy, electrocautery, and laser removal. If the hairs do not contact the cornea, treatment is not usually necessary.
   
   In cases requiring treatment, prognosis is good with proper therapy. Removed hairs may regrow and require additional surgery. Lack of treatment can result in painful eye irritation and permanent scarring of the cornea.
    

   Figure #5: This shows distichiasis where hairs are touching the upper left part of the eye.

    

4. Trichiasis: This condition is similar to distichiasis, in that it is characterized by ocular irritation caused by hairs contacting the cornea and conjunctiva. In trichiasis, the irritating hairs arise from normal areas, not the openings to the meibomian glands. Often it is caused by hair growing on the skin folds near the eyes. The folded skin causes the hairs to be directed toward the eyeball where they contact the cornea and cause irritation. This condition is often seen in flat-faced dogs with well-developed facial folds, such as pugs, bulldogs, and the Pekingese.
   
   Signs of this condition can include a wet face, excessive tearing from the eyes, squinting, and corneal changes including pigmentation and vascularization. These changes will be most noticeable near the inner corners of the eye, because this is the area where the facial hair is often touching the cornea.
   
   Diagnosing this problem is based on physical examination, with observation of the irritating hairs, and lack of other eye disease. Management by trimming the hairs near the eyes may help, or it may worsen the problem if the clipped hair edges continue to contact the cornea. Permanent treatment involves surgery to either remove the facial folds or close the inner corner of the eyelids.
   
   Prognosis is good with treatment. Lack of treatment will allow for continued corneal irritation which causes pain and can lead to corneal pigmentation, scarring, and vascularization. The corneal changes can interfere with normal vision.
    
5. Prolapsed Gland of the Third Eyelid: Also called "cherry eye," this condition is characterized by the prolapse of the gland that typically sits beneath the third eyelid. If the attachment of the gland weakens, the gland can move upward and out of its normal position. It will then become visible as a red, oval bulge protruding just behind the edge of the third eyelid. It is often called a cherry eye due to the visible appearance of the red bulge. It may affect one or both eyes.
    

   Figure #6: This picture shows a typical “cherry eye.”

   This condition may be seen in any dog, but can commonly be found in breeds such as beagles, bloodhounds, bulldogs, cocker spaniels, Lhasa apsos, shih tzus, and other dogs with shortened faces.
   
   The condition is diagnosed on physical examination by the appearance of the red, round to oval mass coming up over the edge of the third eyelid. Accompanying signs can include squinting, repeated blinking, increased tearing, and a reddening of the conjunctiva.
   
   Treatment includes topical medications to reduce swelling and irritation, along with a surgical procedure where the gland is sutured back in place. If replacement is not successful, the gland can be removed, but removal is neither the best nor the first method of treatment. Removal of the gland can result in lack of tear formation that leads to development of corneal and conjunctival problems. Surgical removal is therefore avoided if it is at all possible to replace the gland. Topical therapy with anti-inflammatory eye medication, such as corticosteroids, may be helpful to reduce swelling before surgery and is important as an aid to help the eye heal after surgery. Prognosis is good with prompt surgical repair.
    

6. Blepharitis: Blepharitis is inflammation of the eyelids. It can be caused by any condition that results in inflammation, including allergies, trauma, parasites, immune-mediated disease, endocrine disease, neoplasia, nutritional deficiencies, and infection. Infection can be caused by bacteria, viruses, or funguses. Examples of allergic conditions that may lead to blepharitis include dietary sensitivities, insect stings and bites, and inhalant allergies. Parasitic diseases that potentially cause blepharitis include demodicosis and sarcoptic mange. Additional examples of underlying causes include zinc-responsive dermatosis, fatty acid deficiency, hypothyroidism, diabetes, hyperadrenocorticism, and second-hand smoke. Blepharitis may occur alone, but is often accompanied by inflammation and infection of surrounding tissues leading to conjunctivitis and keratitis.
   
   All dogs can suffer from blepharitis. It may involve one or more lids, and be localized to one spot or involve large areas of the involved lids. Signs may include eyelid spasm, squinting, pain, ocular discharge, discoloration of the lids, hair loss surrounding the lids, redness, crusting, abscesses, pustules, and swelling. There may be concurrent irritation and scarring of the cornea, and redness and swelling of the conjunctiva.
   
   Diagnosis is based on physical examination and specialized tests. A Schirmer tear test, cultures and sensitivities, cytology, skin scrapings, and biopsies may be performed. Underlying conditions such as fungal infections, endocrine disease, parasitic skin infections, bacterial skin infections, and allergies must be diagnosed and eliminated. Once a diagnosis is reached, treatment is designed to eliminate the underlying cause and remove the inflammation from the eyelid. Treatment may involve medications such as antibiotics, antifungals, and anti-inflammatories, along with topical medications that are instilled into the eye and on the lids. Topical therapies may include appropriate antibiotics, corticosteroids, and combination antibiotic-antiinflammatory medications.
   
   Prognosis depends on the cause of the inflammation. Some cases respond rapidly to treatment. Other cases that are caused by whole body (systemic) disease may respond only after treatment of the animal’s underlying problem and may require management for the lifetime of the animal. Proper diagnosis is critical for long-term resolution of blepharitis.
    
7. Tumors of the Eyelid: Growths can occur on the eyelids. The growths most commonly occur in older dogs. Most masses and growths that occur on the eyelids are benign. Those that are malignant tend to invade immediate tissues, but do not typically spread (metastasize) to other places. Common growths include adenomas (meibomian gland tumors), papillomas, melanomas, and adenocarcinomas. Tumors can be confused with localized inflammatory processes that are nodular in appearance.
   
   Dogs with eyelid masses will show various signs depending on the location of the mass. Blepharitis is common. If the mass contacts the conjunctiva, irritation and conjunctivitis will result, leading to signs that include epiphora, ocular discharge, and squinting. If the mass contacts the cornea, corneal irritation and infection may result. This may cause squinting, epiphora, photosensitivity, and other signs of keratitis.
    

   Figure #7: A meibomian gland tumor is present on the upper eyelid of this dog.

   Diagnosis is based upon physical examination. Treatment involves removal of the mass by appropriate surgical techniques, which will vary depending on the size and location of the mass. Reconstructive eyelid surgery may be needed. Prognosis is typically good, but depends on the size and type of the mass. The majority of masses are benign and removing the mass will usually cure the problem. If removal is not complete, many masses will return. Most malignant masses are also controlled by surgical removal.
   

1. Conjunctivitis: Inflammation of the conjunctiva is termed conjunctivitis. Any dog can suffer from conjunctivitis, but those dogs with either underlying allergies or other eye diseases tend to get conjunctivitis more frequently than dogs with normal eyes and no immunological problems. Conjunctivitis may be primary or secondary to other problems. Primary conjunctivitis can be caused by immune-mediated diseases or allergies, as well as foreign objects in the conjunctiva or environmental irritants (dust, chemicals). Primary bacterial or viral conjunctivitis can occur, but is uncommon. The majority of the cases of conjunctivitis are secondary to other eye problems such as keratoconjunctivitis sicca, lid malformations, or nasolacrimal diseases. Others occur following glaucoma, cancer, uveitis, corneal inflammation or systemic immune-mediated diseases. As previously mentioned, distichiasis or trichiasis can lead to conjunctivitis.
   
   Signs of conjunctivitis may include spasm of the eyelids, swelling and redness of the conjunctiva, and discharge from the eyes. The discharge may be clear, mucoid, or mucopurulent. Dogs with conjunctivitis may be sensitive to and avoid the light. They may respond to the conjunctival irritation by pawing at the eyes and rubbing the face and eyes.
    

   Figure #8: This picture shows a dog with severe conjunctivitis.

   Conjunctivitis is diagnosed on physical examination. Additional specific tests are performed to identify other eye problems and to rule out other eye diseases that can lead to conjunctivitis. These include a Schirmer tear test, fluorescein dye, intraocular pressure test, bacterial culture and sensitivity, and if indicated, conjunctival cytology. Steps are taken to identify any underlying or accompanying disease situations that contribute to the conjunctival inflammation.
   
   Treatment involves both medicating the conjunctiva and treating any underlying or secondary problems. For example, dogs with allergic conjunctivitis may need skin testing for inhalant allergies and appropriate immunological therapy (allergy injections), while dogs with a foreign body imbedded in the conjunctiva will require sedation and removal of the object. Dogs with underlying eye disease, such as keratoconjunctivitis sicca, will require long term therapy to modify tear production, while those with an occlusion or blockage of a nasolacrimal duct may respond to a flush of the duct system.
   
   Depending on the cause of the conjunctivitis, treatment may include topical medications to control inflammation and infection, eye washes to remove discharge, lubricants to add moisture to the eye, and medications to control infection and inflammation. Topical therapy may include antibiotic agents, corticosteroids, or combination medications. All discharge should be flushed from the eye before treatment is attempted to allow the medications to contact the surface of the eye and the conjunctiva.
   
   Prognosis depends on the underlying cause and severity of the condition. Simple bacterial conjunctivitis is typically very responsive to treatment with the appropriate antibacterial medications. Secondary conjunctivitis may not respond until the underlying cause is identified and treated. Some secondary conjunctivitis problems may be controlled, but not totally eliminated.
    

2. Keratoconjunctivitis sicca: This disease involves inflammation of the conjunctiva and cornea. It is caused by a lack of proper tear production and is discussed above, under problems of the lacrimal system.

Figure #9: This picture shows severe corneal edema.

1. Abrasions, Lacerations: Any dog can suffer from a traumatic corneal abrasion, scratch, or laceration. Mild injuries can result in a superficial abrasion. Deeper wounds are identified as penetrating or perforating. A penetrating laceration involves the cornea, but does not pass through it. A perforation goes entirely through the cornea.
   
   If wounds are caused by a penetrating or perforating object, the object may still be in the cornea. Wounds can be caused by any object that can contact the eye. Common injuries occur as a result of dogs being hit by pellets from guns, scratched by cats, and running through twigs and branches. Blunt trauma from being hit by a car or running into an immovable object can also lead to lacerations of the cornea. Hunting dogs, dogs that engage in fights with other animals, dogs that commonly run through brush or trees, and dogs that get overly excited are at an increased risk for corneal abrasions and cuts.
   
   Signs of a corneal wound include pain and inflammation of the eye. The eyelids may be kept closed and the dog may resist examination. The wound may be visible on the cornea, along with swelling, cloudiness, and hemorrhage. Facial trauma may also be evident. Diagnosis is made by history and physical examination. An immediate diagnosis can be made if the object that caused the wound is still in the eye. Additional testing is done to determine the severity and extent of the wound, assess vision, and identify trauma to other portions of the eye and face. Bacterial culture and sensitivity may be necessary. A specific test called a fluorescein dye test is performed using special stain to ascertain if the cornea is intact or if it has been perforated.
   
   Treatment depends on the severity, depth, and age of the wound. Care should be taken to apply only minimal pressure to the face and eye to prevent rupture of the eyeball. Any foreign body should be flushed out, removed with a dampened cotton-tipped applicator, removed with forceps, or surgically removed from the eye. Superficial wounds can be treated with topical medications to prevent infections and calm the eye. Topical eye medications include antibiotics and atropine. In addition, an Elizabethan collar or similar collar is used to prevent the dog from scratching the eye as it heals. Activity should be restricted and the dog kept indoors to avoid further injury.
   
   Some lacerations may require additional therapy with a soft contact lens. Extensive corneal lacerations and corneal penetrations require surgical repair. Surgical repair will also be needed for those injuries that contain a foreign body that is not easily removed. All corneal wounds should be rechecked at specific intervals to monitor healing. Superficial wounds can be checked at 3 day intervals; deep wounds should be checked daily for the first several days.
   
   Prognosis depends on the extent of the wound and the time elapsed between injury and veterinary treatment. The deeper the wound, the poorer the prognosis. Most superficial corneal abrasions and wounds heal quickly and satisfactorily. Deeper wounds or those created by blunt trauma may result in permanent loss of vision, inflammation, and pain. The full extent of the damage caused by the wound may not be apparent for days to weeks following the injury, so re-examination is necessary.
    
2. Keratitis: Keratitis refers to inflammation of the cornea. Signs may include swelling (edema), cloudiness, and pigmentation. Keratitis in dogs is typically divided into two major categories. This classification is determined by the presence or absence of ulceration of the cornea.
   
   
   1. Ulcerative Keratitis: This refers to inflammation of the cornea accompanied by ulceration of the surface of the cornea (a corneal ulcer). This is a very common condition in dogs, and all breeds may be affected. Breeds with flat faces may have greater risk of ulcerative keratitis. Ulcerative keratitis can be caused by any condition that disrupts the layers of the cornea, including trauma, entropion, ectropion, trichiasis, keratoconjunctivitis sicca, damage to the nerves of the face, burns caused by chemicals and cleaners, and diseases of the immune system. Infection by bacterial or fungal organisms is uncommon, but may occur secondary to other irritations and injuries.
      
      Ulcerative keratitis is a very painful condition. Signs of disease include tearing (lacrimation), spasms of the lids, pawing at the face, squinting, spilling of tears onto the face (epiphora), avoidance of sunlight (photophobia), redness, and discharge from the eye. One or more defects in the cornea may be visible and are referred to as corneal ulcer(s). Some ulcerative keratitis cases have a mushy, gelatinous appearance as the cornea breaks down due to excessive enzyme production. Chronic ulcers may show vascularization, scarring, pigmentation, and swelling. Healing ulcers may have a hazy, white appearance. Fluorescein dye testing (shown below) helps to determine the depth, severity, and number of ulcers.
       

      Figure #10: The white arrow indicates a corneal ulcer highlighted by fluorescein dye.

      Diagnosis is based on ocular examination and fluorescein dye testing. If needed, specific examination of the interior of the eye and cytology can also aid in the diagnosis. Other tests, such as a Schirmer tear test, are performed to rule out additional or contributory eye diseases.
      
      Treatment involves elimination of the cause, along with specific treatment for the ulceration and inflammation. Underlying eye problems, such as keratoconjunctivitis sicca, entropion, or ectropion, should be treated appropriately. Treatment of the ulcer may include topical antibiotics to prevent infection, topical atropine to control pain, specific medications to control fungal or viral infections, and if indicated, specific medications to prevent collagen breakdown. Dogs may be placed on systemic non-steroidal anti-inflammatory (NSAIDs) medications such as aspirin.
      
      Some ulcers are treated with protective contact lenses. Others may require surgery to trim (debride) the ulcer edges. Additional surgical procedures include punctuate keratotomy, conjunctival flaps, and flaps created from the nictitans. Proper use of an Elizabethan collar or similar device will prevent the animal from scratching the healing ulcer. Eyes should be rechecked at approximately 3-day intervals; those with deep ulcers should be rechecked daily until satisfactory healing is observed.
      
      Refractory corneal ulcers are a group of ulcers that do not heal with traditional therapy. They are also called indolent ulcers, recurrent erosions, and boxer ulcers. Refractory ulcerative keratitis may occur in any breed, but was originally identified in boxers, and the breed is noted for a tendency towards this condition. Refractory corneal ulcers are identified by specific characteristics on ocular examination, which include separation of the corneal epithelium from the underlying corneal layers.
      
      Treatment for these refractory ulcers involves physical and chemical debridement of the ulcer to remove abnormal epithelial tissue and allow healing. Additional surgical therapy includes: nictitans flaps, conjunctival flaps, superficial keratectomy, transplantation of healthy corneal epithelium (keratoepithelioplasty), and multiple punctuate keratotomy. Corneal contact lenses, tissue adhesives, and eye shields made of collagen can also be used. As with other corneal ulcers, topical antibiotics and analgesics are indicated to control infection and pain. Treatment of refractory ulcers can take weeks to months depending on their severity.
      
      The prognosis for ulcerative keratitis depends on the underlying cause, the severity of the ulceration, the type of treatment employed, and response to therapy. Simple, superficial ulcers often heal nicely in approximately one to two weeks. Deeper ulcers treated with surgical techniques may require 4-6 weeks to heal; those treated without surgery may take longer, or never heal satisfactorily. Refractory ulcers may remain unhealed for months unless treated with surgical techniques. After surgery, repair may occur in 2 weeks, and conjunctival flaps may be left in place for a month or longer. Untreated or incorrectly treated corneal ulcers can progress, resulting in rupture of the cornea and loss of vision. This often results in removal of the globe.
       

   2. Nonulcerative Keratitis: This is an inflammation of the cornea that does not result in ulceration. A common disease in dogs, it may occur in any breed following an insult to the cornea that causes inflammation. Inflammation may be caused by an infectious agent, drying of the cornea due to diminished tear production, immune-mediated diseases, or corneal irritation.
      
      Several types of nonulcerative keratitis have been identified, including pigmentary keratitis, chronic superficial keratitis (pannus), neurologic keratitis, nodular granulomatous episclerokeratitis, keratoconjunctivitis sicca, and superficial punctuate keratitis. Signs vary with the specific disease, but can include edema, vascularization, pigmentation, scarring, and deposits of particulate matter in the cornea.
      
      Pigmentary keratitis results in dark brown or black pigment being deposited in the cornea. It is typically found in both eyes. It often begins in the inner corner of the eye and progresses until the pigment diffusely covers the central cornea and even the pupil, resulting in loss of vision. It can be accompanied by increased vascularization and scarring of the cornea. This condition results as a response to chronic irritation, usually caused by problems such as distichiasis, nasal fold trichiasis, entropion, and ectropion. Flat-faced breeds with prominent eyes are prone to pigmentary keratitis. This includes breeds such as pugs, Lhasa apsos, shih tzus, and the Pekingese.
      
      Diagnosis is based on physical examination of the eyes and additional tests to assess tear production. Treatment is aimed at removal of the underlying cause and prevention of further pigmentation. Underlying causes are treated with appropriate medical and surgical therapy. Surgical treatment may include reduction of the nasal folds, removal of abnormal eye lashes, and correction of ectropion or entropion. The keratitis is treated with lubricants and topical corticosteroids as needed. If the condition interferes with vision, the pigmented cornea can be removed via superficial keratectomy or radiation therapy. Prognosis depends on the severity of the condition at diagnosis, and the ability to diagnose and properly treat the underlying cause.
      
      Chronic superficial keratitis is often called "pannus." This is a progressive inflammation of the cornea that can result in blindness. It is found in both eyes. It can occur in any breed of dog, but has a high prevalence in German shepherds. It is also found in Belgian tervurens, Belgian sheepdogs, dachshunds, and greyhounds. It is found in dogs of all ages, and commonly afflicts younger dogs, aged 1-7 years.
      
      Chronic superficial keratitis appears to be more common in areas of intense sunlight or high altitude and is believed to have an immune-mediated cause. The condition is characterized by deposits of reddish-white, pigmented lesions on the cornea. These lesions contain blood vessels and often move across the cornea, starting in the outer, lower corner of the eye and moving inward and upward. Some dogs also develop thickening and pigmentation of the third eyelid. Typically, the lesions are not remarkably painful, but can obscure the cornea, leading to blindness.
      
      Diagnosis is based on ocular examination. Additional testing, such as the Schirmer tear test, is done to rule out contributory eye diseases, including keratoconjunctivitis sicca. Treatment does not provide a cure, but can help control the condition. Treatment involves the use of topical medications such as corticosteroids and cyclosporine, corticosteroid injections below the conjunctiva, Beta-irradiation, and surgery for removal of diseased tissue (superficial keratectomy). Relapse often occurs after surgery, so it is not the treatment of first choice. All treatment is continued for the life of the dog.
       

      Figure #11: The white arrow indicates the side of the eye that has pannus.

      Prognosis is based on severity of the condition, age, and breed of the dog. For example, younger German shepherds have a worse prognosis than those afflicted at an older age. Lack of treatment can lead to blindness in affected dogs. Continuous treatment can allow many dogs to retain vision for their entire lives. Periodic rechecks are recommended to assure that the treatment is effective and to monitor any disease progression.
      
      Neurologic keratitis may occur in dogs that have lost nervous input to the eye, often as a result of trauma. The loss may occur to the sensory nerves, resulting in lack of feeling in the eye, or from damage to the motor nerves, resulting in an inability to close the eyelids. The results are irritation and inflammation of the cornea. Treatment involves the use of ocular lubricants as well as medications to decrease infection and inflammation. Surgery may be performed to close the eye temporarily to allow the nerves to repair. Permanent closure of the lids or removal of the eye may be necessary if the damage to the nerves is permanent.
      
      Nodular granulomatous episclerokeratitis is seen primarily in herding breeds, such as collies, Shetland sheepdogs, and border collies. It is seen in both eyes. It is characterized by the appearance of raised, pinkish lesions on the outer (lateral) part of the cornea. The proliferation of cells occurs typically at the junction of the cornea and the sclera. The lesions are vascular in nature and may appear symmetrical. The disease is believed to be immune-mediated. Treatment involves the use of anti-inflammatory agents, such as corticosteroids or azathioprine. Because the lesions return, surgical removal typically does not cure the problem; therefore, medical control is the treatment of choice.
      
      Superficial Punctate Keratitis: This condition is characterized by a diffuse inflammation of the cornea. The areas of inflammation can be scattered across the cornea. This condition can be caused by viruses, chronic exposure of the eye to the environment, and topical irritants, such as topical anesthetic agents. Diagnosis is based on examination of the cornea. Treatment is based on removal of the underlying cause, along with prevention of infection and reduction of inflammation.
      
      Keratoconjunctivitis sicca is often referred to by its initials, KCS. This condition involves inflammation of both the cornea and the conjunctiva due to insufficient and abnormal tear production. It is discussed above with problems of the lacrimal system.
      
       

3. Corneal Dystrophy: Corneal dystrophy refers to progressive, abnormal changes in the cornea. It is an inherited disorder of the cornea that affects both eyes and can occur in many breeds of dogs. This condition is not associated with corneal inflammation or disease. Different breeds of dogs may have specific types and locations of corneal dystrophy. Some of the breeds with an inherited predisposition to corneal dystrophy include beagles, boxers, Siberian huskies, Chihuahuas, Boston terriers, dachshunds, and Shetland sheepdogs. Many other breeds also have been shown to have a genetic basis for the problem.
   
   Corneal dystrophy is characterized by the formation of non-transparent spots (opacities) in the cornea. The lesions are usually bilateral and may appear symmetrical. They are often gray, white, or silver, and usually round or oval. Corneal dystrophy can affect different layers of the cornea and therefore cause different signs. If the dystrophy appears in the outer layers of the cornea, corneal ulceration can result. (This may be the cause of the refractory ulcerative keratitis described in boxers.) This condition is extremely painful and associated with squinting and eyelid spasm. Those dystrophies that affect the middle or stromal layer of the cornea tend to cause no signs of disease. If the corneal dystrophy appears in the inner layer of the cornea (the endothelium), there may be no signs, or dogs may show pain, loss of vision, ulceration, and corneal edema with advanced cases.
   
   Diagnosis is based on observation of the opacities in the cornea. Additional ocular testing is done to rule out other eye diseases. Fluorescein staining can help identify ulcerations accompanying the dystrophy. Treatment is typically reserved for dogs suffering from ulcerative keratitis. See treatment of ulcerative keratitis above. Those dystrophies that do not cause pain or interfere with vision are not treated. If necessary, lesions can be removed by keratectomy. Lesions may or may not recur following surgery. Some specific dystrophies that affect the endothelium of the cornea are treated with 5% sodium chloride ointment in an effort to prevent ulceration.
   
   Prognosis depends on the amount and extent of the dystrophies and their location in the cornea. The majority of cases of corneal dystrophy do not result in loss of vision. Those that do not interfere with vision or cause pain can be monitored. Prognosis for those contributing to refractory ulcerative keratitis varies with the severity of the disease.
   
   

1. Lenticular Sclerosis: Lenticular sclerosis, also called nuclear sclerosis, is a normal aging change in older dogs. It is commonly seen in dogs 7 years of age or older. As the dog ages, the lens thickens and becomes less flexible. This thickening creates haziness in the eye that can be confused with cataract formation. Light will pass through a sclerotic lens; the cloudiness does not obscure vision. Nuclear sclerosis can be differentiated from a true cataract on ocular examination. No treatment is necessary.
    
2. Cataract: Cataracts are a very common condition in many breeds of dogs. Cataracts refer to either opacities within a lens or an entire lens that is opaque. The term cataract means "to break down," referring to the loss of normal architecture of the fibers in the lens or its capsule, resulting in an increase of fluid in the lens and loss of transparency. Cataracts are hereditary in many breeds. Some breeds with a high incidence of cataracts include cocker spaniels, Great Pyrenees, Irish wolfhounds, West Highland white terriers, Chesapeake Bay retrievers, Shetland sheepdogs, miniature schnauzers, Labrador retrievers, Old English sheepdogs, golden retrievers, Boston terriers, Siberian huskies, Staffordshire bull terriers, golden retrievers, Afghan hounds, and poodles. There are many other breeds with a genetic predisposition to cataracts. In breeds with hereditary cataracts, the cataracts may appear at any age and are often seen in younger dogs. The type of cataract and age of onset is breed specific and can be associated with other eye abnormalities.
   
   Although most cataracts are hereditary, other factors can contribute to the formation of cataracts. These can include metabolic diseases, trauma to the globe, exposure to toxins, radiation therapy performed near the eyes, certain amino acid deficiencies, and inflammatory diseases such as uveitis. The most common cataract seen secondary to metabolic disease is found in dogs with diabetes mellitus. It is hypothesized that all dogs with diabetes mellitus will eventually develop cataracts. Onset is relatively rapid and the cataracts develop simultaneously in both eyes. Young animals fed diets low in calcium or in amino acids can also develop cataracts.
   
   Although cataracts can be seen early in their development, most owners do not notice any signs of cataracts until the dog loses sight. Owners may not notice the loss of vision if the dog gradually adapts to the loss, but will be aware of a problem if the dog becomes totally blind. Not all cataracts develop to the point where they cause blindness. Diagnosis is made by examination of the eyes. Cataracts can be classified by location in the lens and degree of development. Examination of the retina should accompany any examination for cataracts.
    

   Figure #12: This picture shows the loss of transparency in an eye with a cataract.

   Treatment is reserved for cataracts that cause blindness. There is no effective medical therapy. A limited number of cataracts will spontaneously resorb. Spontaneous cataract resorption is an unpredictable process that may or may not result in improved vision. It tends to occur in certain breeds of dogs and in animals that are under 6 years of age. It is not advisable to delay treatment while attempting to wait for spontaneous resorption. Treatment involves surgical removal of the lens. The lens can be replaced with a prosthetic lens if desired. Although several techniques can be used, phacoemulsification is commonly used today. This technique involves the use of a small ultrasonic probe that is placed into the eye. It shatters the cataract and then removes the broken-down debris by suction.
   
   Prognosis depends on the severity of the cataract, the cause of the cataract, and the time between identification and surgical removal. Success rates with phacoemulsification are greater than 90%. The best prognosis is associated with hereditary cataracts treated early in their course. The worst prognosis is associated with long standing cataracts that are found in conjunction with other ocular problems, such as uveitis or degeneration of the retina. Dogs with retinal degeneration are not candidates for cataract removal because they will not regain sight after the procedure.
    

3. Luxation and Subluxation of the Lens: This occurs if the lens separates from the zonules that hold it in position. A partial separation results in a subluxation of the lens, leaving the lens either in or near its normal position. A total luxation results from a complete rupture of the zonules and total separation of the lens. The lens will then displace either into the anterior or posterior chamber. This condition can occur either by itself or secondary to intraocular problems including uveitis, glaucoma, neoplasia, or trauma. The condition is more commonly seen in certain breeds, including poodles, border collies, spaniels, the shar-pei, miniature schnauzers, Jack Russell and other terriers, Norwegian elkhounds, and beagles. These dogs may have genetically weak zonules that easily tear apart with trauma, aging, or altered pressure in the eyeball.
   
   Signs of lens subluxation or luxation vary depending on the degree of lens movement and its location. A subluxation may not result in signs that are noticed by the owner. Luxation may result in a painful eye with photophobia, edema of the cornea, cloudiness of the cornea, and redness. Examination of the eye reveals changes in the depth of the anterior chamber of the eye, iridodonesis (the iris moves rapidly or trembles when the eye is moved) and an aphakic crescent. An aphakic crescent is a crescent-shaped area of the pupil that is lacking the lens. This occurs because the luxated lens is no longer sitting directly behind the pupil, but has shifted its position. Other eye conditions, such as glaucoma or uveitis, may be present.
   
   Diagnosis is based on ocular examination. The anterior chamber will be abnormally deep or shallow and the aphakic crescent will be present. Iridodonesis will be observed. Additional tests for ocular disease may be performed, including pressure tests for glaucoma and dilation of the eye to check for other abnormalities. Because lens luxation can occur in both eyes, the "normal" eye should also be examined.
   
   Treatment depends on the location and displacement of the lens. Subluxations may not require any treatment, except for continual monitoring. Subluxated lenses can progress to total luxations or contribute to glaucoma. Lenses that have displaced into the posterior chamber of the eye may be managed with topical medications, such as 0.125% demecarium bromide, that keep the pupil contracted.
   
   The majority of luxated lens are treated with surgical removal. If surgery is delayed, topical anti-inflammatory medications, such as 0.1% dexamethasone, are indicated, along with medications to reduce intraocular pressure and prevent glaucoma. These include dichlorphenamide, a carbonic anhydrase inhibitor. Surgery should be performed as soon as possible to prevent loss of vision. If accompanying glaucoma has resulted in blindness or a neoplasia is present, treatment may involve removal of the eye.
   
   Prognosis depends on the degree of displacement and location of the lens, accompanying ocular disease, and time between onset of the problem and treatment. The best prognosis is reserved for those cases that are treated early after onset with surgery and do not have accompanying glaucoma. The poorest prognosis accompanies those cases with glaucoma and a delay between onset and treatment.
   

Because the uvea is highly vascular, it is very reactive to changes in the body and is easily inflamed. Inflammation of the uvea is called uveitis. Specifically, inflammation of the iris and ciliary body is termed anterior uveitis. Posterior uveitis refers to inflammation of the choroid. Inflammation may be limited to only the anterior or posterior uvea, or involve both portions. Inflammation of the uvea allows particles to cross the blood-aqueous barrier and enter the aqueous humor. This causes an inflammatory response in the aqueous which can lead to a reduction or total loss of vision.

1. Anterior uveitis: Inflammation of the anterior uvea may occur with several disease conditions seen in the eye. The cause may be external to the eye and include trauma. In addition, anterior uveitis may follow corneal injuries and corneal ulceration. Anterior uveitis can also be caused by infectious agents such as viruses, bacteria, funguses, protozoa, parasites, and rickettsia. These infections can be limited to the eye or cause disease throughout the body.
   
   Some whole body (systemic) diseases that may be associated with uveitis include Lyme disease, leptospirosis, blastomycosis, toxoplasmosis, and Rocky Mountain spotted fever. In addition, metabolic diseases such as diabetes, certain immune-mediated diseases, eye neoplasia, and exposure to some toxins may lead to anterior uveitis. The "blue-eye" that has been seen in dogs after some adenovirus vaccinations is uveitis.
   
   Signs of anterior uveitis may include pain, redness of the conjunctiva, corneal edema, red blood cells or white cells in the anterior chamber, epiphora, spasm of the eyelids, and aversion to light. Other ocular changes are specific to anterior uveitis. These include constriction of the pupil, a change in the color of the iris (often darker), swelling of the iris, and enlargement and engorgement of deep blood vessels located in the ciliary body. In addition, inflammatory cells and pigment may clump together and adhere to the cornea, forming small, visible masses called "keratic precipitates." As particles form or flood into the inflamed area, the aqueous humor becomes turbid. This condition is referred to as "aqueous flare." In chronic cases, the iris may actually adhere to the lens, "fixing" the pupil in an unmovable position. This results in a distorted and immobile pupil. Finally, anterior uveitis can be associated with other serious eye problems, including lens luxation, cataracts, ulcerative keratitis, and secondary glaucoma.
    

   Figure #13: This picture shows an eye inflicted with uveitis.

   Diagnosis is based upon complete physical and ocular examination. A thorough eye examination includes measurement of the intraocular pressure. The pressure is typically decreased with uveitis. Additional testing may include blood testing, urinalysis, and radiographs to search for the underlying cause of the disease.
   
   Treatment is aimed at reducing the inflammation of the uvea while determining and eliminating the underlying cause. Anti-inflammatory agents including corticosteroids (1% prednisolone acetate, 0.1% dexamethasone) and non-steroidal anti-inflammatories (flurbiprofen) can be applied topically. Topical medications that dilate the pupil are also used (atropine). In some cases, corticosteroids can be injected under the conjunctiva or administered systemically. Those patients that do not respond to corticosteroids can be treated with other immunosuppressive drugs, such as azathioprine. Treatment may be altered depending on the cause of the uveitis and the systemic illnesses that are present. Treated animals should be re-examined within one week following the initial treatment and re-evaluated every few weeks.

   Prognosis depends on the severity of the uveitis at the time of treatment and the underlying cause of the uveitis. Early, aggressive treatment of the uveitis and the initiating cause is necessary to prevent secondary problems. Prognosis is good if the underlying cause is identified and eliminated, and appropriate eye therapy is instituted. If uveitis is left untreated, glaucoma, lens luxation, and blindness can result. Successful treatment can involve several months of continual medication and follow-up examinations.
   
   
   

Introduction: The retina is the back portion of the eye. It is considered the "film" that records the visual images that come through the cornea and are focused by the lens. The cells of the retina receive the light images. These cells are of two main types, rods and cones. The rods are sensitive to dim light and the cones are sensitive to bright light. The rods are useful at dusk, while the cones perceive images in the day and help distinguish colors.

The rods and cones translate the light images into chemical messages which affect adjacent nerve fibers. The retinal nerve fibers converge together at an area called the optic disc to form the optic nerve. The messages travel as nerve impulses along the optic nerve to the brain where they are again converted into visual images. Any type of damage to the retina will result in interruption of this process and cause loss of vision.

1. Degeneration of the Retina: If the retina degenerates or atrophies, messages from the eye will no longer reach the brain and blindness will result. Conditions such as trauma, infection, neoplasia, retinal detachment, malnutrition, glaucoma, and inflammation can lead to degeneration of the retina. In many cases, retinal degeneration is a primary condition that is inherited in dogs.
   
   The most common form of retinal degeneration is called progressive retinal atrophy or PRA. This is not a single disease, but a variety of metabolic and chemical processes that result in atrophy or degeneration of the retina. Individual breeds demonstrate different types of retinal degeneration that can be characterized by changes in different, specific processes and cells in the retina.
   
   It is possible to categorize PRA by the breed afflicted, the age of onset, and the particular cells affected. Dogs are commonly classified as having early-onset or late-onset PRA. Early-onset PRA is termed "retinal dysplasia," meaning that the retina never formed correctly. Breeds such as Irish setters, collies, Norwegian elkhounds, and miniature schnauzers suffer from early onset PRA, often showing signs as early as 3-4 months of age. Other dogs show signs much later. Dogs that are born with fully formed retinas that later degenerate are suffering from "retinal degeneration." These breeds, such as akitas, poodles, cocker spaniels, miniature long-haired dachshunds, Samoyeds, and Labrador retrievers suffer from late-onset PRA, and may not show signs until they are 4 years of age or older.
   
   No matter the exact cause of PRA, the signs of retinal degeneration are the same. In the early stages of PRA, dogs may not show many signs. As the retina’s cells degenerate, the dog loses vision. If the dog adapts to the loss of vision, owners may not notice the change until late in the course of the disease. Dogs typically lose night vision first, so the animals may have difficulty in dimly lit rooms or at night. This problem can go unnoticed by an owner that leaves on indoor lights until retiring for the evening. Eventually, the retinal atrophy will progress and total blindness will result. An owner may be aware of dilated pupils or a shine from the back of the dilated eye, or may notice nothing until the animal has totally lost vision. Some animals may develop other eye changes, such as cataracts.
   
   Diagnosis is based upon ocular examination. Pupils will be dilated and not responsive to light. The retinal area will be hyperreflective and retinal examination will show degeneration of the retina and optic nerve, along with changes in the retinal blood vessels and pigmentation. A test called an electroretinography can be performed to measure electrical activity in the retina. Depending on the breed, different areas of the retina will be affected.
   
   There is no successful treatment for PRA. The condition is not painful and most dogs successfully adapt to the loss of sight. Dogs can be helped with their adjustment by being confined to a fenced yard and walked on a leash. Furniture should be left in one place so that pets can memorize its location. Applying a scent, such as perfume, to the furniture can help the dog identify and locate it.
   
   Owners of breeds at risk for this condition should have their pets examined and screened for the disease by a veterinary ophthalmologist. The proper age for screening is determined by the breed of dog. Affected dogs should be removed from the breeding population.
    
2. Detachment of the Retina: The retina is composed of 10 layers. If these layers separate, the retina literally pulls apart, or "detaches." The separation of the retinal layers interferes with the collection of light and reduces nervous input to the optic nerve. This results in loss of vision, and potentially, total blindness. The retina may be detached by trauma. Traumatic injury can include severe blunt trauma that causes bleeding into the eye or sharp trauma caused by a penetrating foreign body. Non-traumatic causes of detachment of the retina include lens luxation, drug reactions, retinal atrophy, high blood pressure, neoplasia, cataracts, cataract surgery, retinitis, metabolic diseases, and immune-mediated diseases. Certain breeds are prone to develop the problem, with the condition being found more commonly in those breeds that suffer from lens luxation, progressive retinal atrophy, and cataracts. In addition, the shih tzu, miniature dachshund, and miniature poodle may suffer from spontaneous detachment.
   
   Signs of a detached retina include partial or total loss of vision. Diagnosis is based on ocular examination. Ocular examination will reveal a dilated pupil that does not respond normally to light. The blood vessels and folds of the detached retina will be visible behind the lens. In addition, any fluid which accumulates between the torn layers of the retina will be visible. Additional testing can be done to check for systemic causes such as elevated blood pressure, infection, neoplasia, and auto-immune disease. The type of testing will be determined by what is suspected as an underlying cause.
   
   Treatment should be started immediately. Treatment is dependent upon the underlying cause and may include anti-inflammatory drugs, antibiotics, and potentially, surgical repair. Prognosis is dependent on the underlying cause and the time elapsed between onset and treatment. Retinal detachment can be reversible with appropriate treatment of the underlying cause. Prognosis is typically guarded for return of complete vision, even if spontaneous reattachment does occur. Animals with a retinal detachment in one eye should have the other eye monitored, because the potential exists for the other eye to develop similar problems.
   
   

Introduction: Cancers may develop in any structure in the eye. They can be found in any age or breed of dog, but are generally more common in older animals.  A cancer may be primary and arise from tissue in the eye, or be secondary to a cancer somewhere else in the body. Cancers located anywhere else in the body may migrate (metastasize) to the eye. Tumors may be localized nodules or locally invasive. In addition to occupying space, tumors may cause infection and inflammation of involved tissues. Common eye tumors include adenomas, adenocarcinomas, papillomas, melanomas, histiocytomas, squamous cell carcinomas, and fibromas. Tumors are more likely to be found on the eyelids than any other part of the eye.

A mass in or near the eye will cause signs that reflect the involved area of the eye. For example, dogs that have a mass on the lid or conjunctiva will demonstrate signs of blepharitis and conjunctivitis. A mass located on the retina may cause blindness and a dilated pupil. Signs associated with eye disease are not specific to one diagnosis, so ocular examination and diagnostic tests are necessary for proper diagnosis. Diagnostic tests may include special examination, biopsy, histopathology, and MRI testing. Microscopic examination will allow differentiation between inflammation, benign tumors, and malignant tumors. Treatment depends on the type and location of the growth and may include surgical removal, chemotherapy, and removal of the eye. Prognosis is dependent on the location and type of growth. Early identification and removal of malignant tumors will increase the probability of a successful outcome and reduce the risk of tumor spread.

* All of the pictures were used with permission from Colorado State University Ophthalmology Service.

Introduction: Eye medications can be delivered by several methods. Topical medications are applied directly to the eye surface. The topical medications may be available as eye drops and ointments. This method of administration is appropriate for both hospital and home treatment of eye diseases in dogs. In addition, veterinarians may administer medications via injection into the eye. Common sites for these injections are subconjunctival (beneath the conjunctiva), retrobulbar (behind the eye), or intraocular (into the eyeball).

In addition, diseases of the eye may be treated with medications that are given directly to the dog, either by mouth or by injection. Finally, eye diseases may not be limited to the eyes; they may be a sign of disease that is affecting the entire body. In this case, the veterinarian will prescribe medication to treat the primary illness, as well as to control the problems in the eyes.

The following table lists commonly used eye medications. Depending on the combination of related eye problems present at one time, a specific medication may need to be combined with other medications or be inappropriate for its original, intended use. All eye medications should be used under the guidance of a veterinarian. Page B224 of this manual has information on how to properly clean the eye and administer products.