F220
Eye Diseases and Problems

Introduction: It is important to examine an animal’s 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. Some animals may rub the eye 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 most problems. Tests may include a fluorescein dye test, a Schirmer tear test (testing for tear production), 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 cattle 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 of the eye.

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 ulceration - An open lesion or sore on the surface of the cornea.
15. Enucleation - Removal of the eye.
16. Epiphora - The abnormal flow of tears over the face.
17. Fibrous - Composed of cells that form tough, connective tissue.
18. Fluorescein dye - A special dye that is applied to the cornea that will not penetrate intact cornea or conjunctiva, but will adhere to and outline areas of ulceration.
19. Glaucoma - Increased ocular pressure resulting from altered flow of aqueous humor.
20. Globe - The eyeball.
21. Intraocular - Within the eyeball.
22. Iris - The colored, circular portion of the eye located behind the cornea. It is part of the uvea.
23. Keratitis - Inflammation of the cornea.
24. Keratoconjunctivitis - Inflammation of the cornea and conjunctiva.
25. Lacrimal apparatus - The structures in the eye responsible for tear production.
26. 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.
27. Lens luxation - Displacement of the lens.
28. Miosis - Contraction of the pupil so that the pupil becomes small.
29. Miotic - A medication that causes the pupil to become small.
30. Mucoid - This is a general term for types of secretions that are made up of mucous materials.
31. Mucopurulent - A secretion or exudate that is made up of pus and mucous.
32. Mydriatic - A medication that causes the pupil to become large.
33. Mydriasis - A dilated pupil.
34. Nasolacrimal - The system of the eye responsible for proper drainage of tears out of the eye and into the inside of the nose.
35. Nictitans (nictitating membrane) - The third eyelid.
36. Ophthalmoscope - A device for studying the interior of the eyeball.
37. Optic nerve - The nerve that originates from the retina and carries light signals to the brain.
38. Posterior uvea - The portion of the uvea made up of the choroid.
39. Posterior uveitis - Inflammation of the choroid.
40. Pupil - The circular opening in the center of the iris through which light passes into the eye.
41. Primary - The first, or foremost. Used in this case to describe problems that occur first and may be followed by other, secondary problems.
42. Proptosis - Prolapse of the eye.
43. Retina - The innermost coat of the eye, formed of cells sensitive to light.
44. Retinal degeneration - A progressive, pathological change that interferes with the function of the retina.
45. Schirmer tear test - A method of measuring tear production using small strips of absorbent paper placed into the lower corner of the eye.
46. Sclera - 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.
47. Secondary - A problem or disease which occurs after the first or primary disease or problem.
48. Tonometry - The measurement of intraocular pressure.
49. Topical - Medication that is applied locally on an external portion of the eye.
50. 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.
51. Uveitis - Inflammation of the uvea.

Figure #1: Vertical cross-section of the eye      . Anterior chamber Cornea Suspensory ligament Ciliary body Sclera Choroid Vitreous chamber Optic disc Retina Lacrimal gland Eyelid Pupil Iris Lens

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

Problems with the lids can result in pain, swelling, redness, excessive tearing, and drainage from the eye. Animals with lid pain may attempt to rub their eyes, 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 rare 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 animal, but is most often seen in young animals soon after birth.
   
   Treatment involves eye medications to help calm the irritate eye. 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.
    
2. Ectropion: This is a rolling out of the eyelids. The outward turning, which is called eversion, 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 is also rare in cattle.
   
   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.
   
   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.
    
3. Dermoids: These are growths that can occur on the eye. They are present at birth and may involve the eyelid. The surface of the growth often contains hairs. Surgical removal is the only treatment. See figure #2.
    

   Figure #2: The white arrow identifies a dermoid on the surface of the cornea.

   
   
4. Blepharitis: Blepharitis is inflammation of the eyelids. It can be caused by any condition that results in inflammation. In cattle, the most common causes of blepharitis are viral and bacterial infections. Conditions such as trauma, parasites, and neoplasia can also cause blepharitis. Blepharitis may occur alone, but is often accompanied by inflammation and infection of surrounding tissues leading to conjunctivitis and keratitis.
   
   All animals 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. Cultures and sensitivities, cytology, skin scrapings, and biopsies may be performed to help in the diagnosis. Underlying conditions such as parasitic skin infections and bacterial skin infections 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 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/anti-inflammatory medications.

Exopthalmos - The term exopthalmos refers to a condition where the eye is pushed out away from the face in an abnormal fashion. This condition can be caused by abscesses that from behind the eye or cancerous tumors (lymphosarcoma and squamous cell carcinoma) that physically force the eyeball outward. Treatment for this condition may involve removing the eye and as much of the tumor as possible. Abscesses should be lanced and drained.

Problems affecting the conjunctiva may be limited to only the conjunctiva or may involve other portions of the eye. Conjunctival inflammation or disease may also signal illness that affects the entire body. It is important to recognize whether disease processes are limited to the conjunctiva, extend to other parts of the eye, or signal whole body (systemic) disease.

1. Conjunctivitis: Inflammation of the conjunctiva is termed conjunctivitis. Any animal can suffer from conjunctivitis. Conjunctivitis may be primary or secondary to other problems. Primary conjunctivitis can be caused by trauma (feeding coarse forage in a deep manger or over-head feeder), foreign objects in the conjunctiva, or environmental irritants (wind, dust, chemicals). Bacterial and viral infections commonly cause conjunctivitis in cattle. Bacterial organisms such as Moraxella bovis (pinkeye), Mycoplasma, Hemophilus somnus, and Listeria monocytogenes can cause the infection and conjunctivitis. Viral infections of malignant catarrhal fever and infectious bovine rhinotracheitis will also cause conjunctivitis. Problems in the eye can also be caused by eye worms (Thelazia). These eye worms are spread by face flies and other flies of the Musca family when they feed on eye secretions. Conjunctivitis can also be secondary to other eye problems such lid malformations, nasolacrimal diseases, glaucoma, cancer, uveitis, or corneal inflammation.
   
   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. Animals with conjunctivitis may be sensitive to and avoid the light (photophobia). They may respond to the conjunctival irritation by rubbing the face and eyes.
   
   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. 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 systemic 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.
   
   Most bacterial infections in cattle can be treated with topical tetracycline and long-acting injectable products given in the muscle. Because of their ability to remain in the eye, ointments are the preferred topical treatments. The ointment should be applied to the eye 3-4 times a day until the conjunctivitis is corrected. If eye worms are suspected as the cause for the problem, the worms can often be removed with forceps after topical anesthesia has been applied to the eye. In cattle, reports indicate that systemic ivermectin and levamisole are effective at controlling eye worms. Fly repellants and sprays are also important in the prevention of eye worms.
   
   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.

1. Abrasions, Lacerations: Any animal 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. The same things that can cause conjunctivitis (feeding on coarse hays, bacterial infections, etc.) can also lead to corneal lesions.
   
   Signs of a corneal wound include pain and inflammation of the eye. The eyelids may be kept closed and the animal may resist examination. The wound may be visible on the cornea, along with swelling, cloudiness, and hemorrhage. 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.
    

   Figure #3: The white arrow indicates a foreign body in the cornea. The foreign body has also caused some corneal edema that makes the eye appear cloudy.

    

   Figure #4: The white arrow indicates a different type of foreign body found in the cornea of this eye.

   
   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.
   
   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.
   
   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 all animals.
   
   Ulcerative keratitis can be caused by any condition that disrupts the layers of the cornea, including trauma, entropion, ectropion, trichiasis, keratoconjunctivitis, damage to the nerves of the face, and burns caused by chemicals and cleaners. Infection by bacterial or viral organisms 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, 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 ulcers. Some ulcerative keratitis cases have a mushy, gelatinous appearance as the cornea breaks down due to excessive enzyme production; this is sometimes called a "melting" ulcer. Chronic ulcers may show vascularization, scarring, pigmentation, and swelling. Healing ulcers may have a hazy, white appearance. Fluorescein dye testing helps to determine the depth, severity, and number of ulcers.
   
   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.
    

   Figure #5: A Pseudomonas infection has caused an ulcer to form in the corner of this eye.

   
   Treatment involves elimination of the cause, along with specific treatment for the ulceration and inflammation. Underlying eye problems, such as keratoconjunctivitis, 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 viral infections, and if indicated, specific medications to prevent collagen breakdown. Animals may be placed on systemic non-steroidal anti-inflammatory (NSAIDs) medications such as aspirin or banamine.
   
   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. Eyes should be rechecked at approximately 3-day intervals; those with deep ulcers should be rechecked daily until satisfactory healing is observed.
   
   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 1-2 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, healing 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.
    

3. Infectious Bovine Keratoconjunctivitis (pinkeye): The term keratoconjunctivitis refers to inflammation of the cornea and conjunctiva. A very common type of keratoconjunctivitis found in cattle is a condition often referred to as pinkeye. Pinkeye is usually a bacterial infection that leads to keratoconjunctivitis. Pinkeye is not the only cause of keratoconjunctivitis in ruminants. For additional information on pinkeye, refer to page F635 of this manual.
   
    

   Figure #6: This is a picture of a typical pinkeye infection. Notice the redness and irritation found on the under surface of the eyelid and on the conjunctiva.

Introduction: The lens focuses light waves that come through the pupil. It is held in place by small suspensory ligaments called lens zonules that attach the lens to the ciliary body. The ciliary body can contract and relax, thereby changing the shape of the lens. The changing shape of the lens allows it to properly focus light waves from different distances onto the retina.

Cataract: 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 in cattle can be caused by infectious agents (bovine viral diarrhea virus ) or can be the result of aging (less common in cattle due to short life span). Some cataracts are present at birth and are often associated with bovine viral diarrhea (BVD) infections. Things such as metabolic diseases, trauma to the globe, exposure to toxins, and inflammatory diseases such as uveitis can also cause cataracts. 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.

Treatment is reserved for cataracts that cause blindness. There is no effective medical therapy. Treatment involves surgical removal of the lens. Because of the complicated and expensive nature of this surgery, it is not commonly done in large animals. 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.

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.

Uveitis: Inflammation of the uvea may occur with several disease conditions seen in the eye. The cause may be external to the eye and include trauma. In addition, uveitis may follow corneal injuries and corneal ulceration. Uveitis in cattle can be caused by infectious agents such as Mycobacterium bovis (tuberculosis), neonatal septicemia, and malignant catarrhal fever (MCF) These infections can cause disease not only in the eye, but throughout the body.

Signs of 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, uveitis can be associated with other serious eye problems, including cataracts, ulcerative keratitis, and secondary glaucoma.

Figure #7: This is a picture of an eye that has anterior uveitis. Notice how the surface of the eye (cornea) is clear, but there seems to be some cloudiness deeper in the eye.

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 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 can be applied topically. Topical medications that dilate the pupil (atropine) are also used. In some cases, corticosteroids can be injected under the conjunctiva or administered systemically. 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.

1. Infectious Bovine Rhinotracheitis (IBR): IBR is caused by a herpes virus that can cause problems with the reproductive tract, the respiratory tract and also the eyes. When IBR infects the eyes, conjunctivitis is the most common sign. The eyes may initially have excessive tearing and even an infectious looking discharge. The conjunctiva around the eye and eyelids becomes inflamed, swollen and red. Small white dots or plaques may appear on the conjunctiva after 1-2 weeks of infection. If corneal changes do occur, they are found around the outer edge of the cornea. This is one way to differentiate IBR infections from Moraxella bovis (pinkeye) infections where corneal lesions are usually found in the center of the eye.
   
    

   Figure #8: This is an example of an eye that has been infected with IBR.

    

   Figure #9: This is a picture of a calf that was infected with IBR.

    

   Figure #10: This is a third example of an eye that has been infected with IBR.

   
   If IBR is suspected, swabs from the eye can be taken during the first 7-9 days of the initial infection. These swabs can be tested for the virus. Most cases of IBR conjunctivitis will resolve within 10-20 days and treatment is not usually necessary. If treatment is chosen, antibiotic eye ointments are often given. The best way to prevent IBR eye infections is through vaccination. Page F355 has some additional information on IBR in cattle.
    

2. Bovine Viral Diarrhea (BVD): BVD is caused by a virus that can affect many parts of the body. Studies show that if a pregnant cow becomes infected with BVD during the first quarter to half of her gestation, the calf can be born with central nervous system problems and eye abnormalities. Calves born with BVD related eye problems are often blind. They can have cataracts and other problems that make the lens of the eye appear very white (leukocoria). Problems with the retina and optic nerve are also common. Severely affected calves rarely make it full term or are often born dead. Additional details about BVD infections can be found on page F100 of this manual.
    
3. Malignant Catarrhal Fever (MCF): MCF is caused by a virus that causes many different problems in cattle. Inflammation of the nose, mouth and eyes is a common sign. When the eye is involved, there will be excessive tearing, severe conjunctivitis, and inflammation of many parts of the eye. The cow may avoid the light (photophobia) and the eye may appear cloudy. MCF eye infections appear more severe than IBR or BVD infections and cause significant changes to the inside of the eye (anterior uveitis). Many animals with eye problems caused by MCF will not regain normal sight. See page F497 for more information on MCF.
   
    

   Figure #11: This cow eye has suffered significant damage as a result of a MCF infection. Notice how almost every part of the eye is involved.

1. Ocular Squamous Cell Carcinoma (Cancer Eye): Cancer eye is the most economically significant and most common type of cancer found in cattle. It causes the vast majority of carcass condemnations at slaughter. At first, most areas of squamous cell carcinoma around the eye appear as small, white bumps or wart-like lesions. These often progress into more malignant tumors that appear pink and often ulcerated. These tumors can be almost any size and often invade the eye structures and surrounding bone and tissues. If left long enough, the tumor will spread to other areas of the body.
   
   Cancer eye in cattle is directly related to skin color and sun exposure. Tumors develop when light colored areas of skin around the eye are exposed to excessive sunlight. Cattle with white faces and light skin pigments around the eyes are very susceptible to this type of cancer. The most common treatment is complete removal of the eye and surrounding tissues. Most animals with confirmed cases of cancer eye should be culled.
    

   Figure #12: The black arrow points to an area of squamous cell carcinoma on the inside corner of this eye.

    

   Figure #13: This eye also has an area of squamous cell carcinoma on the inside corner of the eye.

   
    
2. Lymphosarcoma or Malignant Lymphoma: Lymphosarcoma is a very common type of cancer found in cattle. In most cases, the cancer can cause problems throughout the body and also problems with the eye. When an eye becomes involved, the most common sign is a bulging outward of the eye (exopthalmos). The eyeball is physically pushed out of the eye socket by neoplastic cells. With time the eye can develop keratitis and other serious eye problems.
   
   Because lymphosarcoma is a systemic or whole body disease, by the time eye problems are noticed, the animal will have other lesions in the body. This means that simply removing the eye will not cure the problem. In most cases the cow is culled and will probably not be fit for slaughter and consumption. Additional details about lymphosarcoma can be found on page F80 of the beef manual.

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

Eye Medications: 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 farm treatment of eye diseases in cattle. 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 animal, 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.

Summary: The eye is a complex structure that processes images for transfer to the brain. It is composed of several interrelated structures. A problem that affects any portion of the eye can result in loss of vision. A problem that affects one portion of the eye may also affect adjacent structures. Because different disease processes can cause the same signs in the eye, examination by a veterinarian is necessary for proper diagnosis and treatment. Prompt examination and treatment can prevent severe, progressive disease. Animals should be examined by a veterinarian at the first sign of any eye problem.

The following tables list 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 may be inappropriate for its original, intended use. All eye medications should be used under the guidance of a veterinarian. Page B220 of this manual has information on how to properly clean the eye and administer products.