Eye Disorders in Dogs and Cats
Contents:
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Cataract 
Collie Eye Anomaly 
Conjunctivitis 
Corneal Injuries 
Disorders of the Nasolacrimal Drainage 
   Apparatus 
Distichiasis and Trichiasis 
Ectropion 
Entropion 
Enucleation 
Epiphora 
Glaucoma 
Keratitis 
Keratoconjunctivitis Sicca 
Nictitans Gland Protrusion 
Pannus 
Progressive Retinal Atrophy 
Ulcerative Keratitis  
Uveitis 
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Cataract
General Information:
A cataract is any abnormal opacity (cloudiness) of the lens or its outer covering (capsule).  The opacity may range from a tiny spot to a total loss of transparency.
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The lens is an M&M-shaped transparent structure that lies directly behind the iris and pupil.  The cornea, aqueous humor, lens, and vitreous body are elements that bend (refract) light waves to form an image upon the retina.  The cornea accounts for about 80% and the lens for 20% of the light-bending action.
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Causes of cataracts, include heredity, metabolic defects, injuries, and aging.  The rate of cataract development ranges from a few days to years.
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Lens removal (cataract surgery) in animals is not as successful as in people, due to structural and physiologic differences between people and animals.  Also, normal animal behavior can result in post-surgical injury, while people can be told to observe certain precautions.  Artificial lenses are usually not necessary after surgery; however, they have shown some benefit in selected cases.   Some animals do not see for several weeks after surgery; others see after a few days.  Some pets may not be suitable for cataract surgery due to age, health, and psychological make-up.  If your pet should not undergo surgery, do not be discouraged, since it will probably be an acceptable pet despite its handicap.


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Collie Eye Anomaly
General Information:
Collie eye anomaly (CEA) is an inherited and incurable disorder of collies.  It may be detected with the aid of special eye instruments at 5-8 weeks of age.  It affects both eyes, and one eye may be more seriously affected than the other.  Generally, the disorder does not worsen as the dog ages unless the retina detaches.  Retinal detachment may occur in serious cases and usually results in blindness of that eye.  Fortunately, retinal detachment does not often occur.
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Affected dogs have less than normal vision, and unless very severe, it is difficult to tell by their actions.  In other words, most collies with Collie Eye retain adequate functional vision.  Collie Eye goes undetected in many instances.
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Only selective breeding of normal animals will significantly reduce the incidence of Collie Eye.  It is an autosomal recessive trait, which means that both parents must be genetic carriers of the defect for it to show up in their pups.
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Some Descriptive Terms:


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Conjunctivitis
General Information:
The conjunctiva is the pink tissue that lines the inner surface of the eyelids and covers the front portions of the eyeball except the clear transparent cornea.  It is a protective layer that contains special glands whose secretions help maintain normal eye health.
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Conjunctivitis is used to describe the conjunctiva when it becomes reddened, congested, and painful.  It may occur in one or both eyes, depending upon the cause.  Causes of conjunctivitis include foreign matter, chemicals, bacteria, viruses or other germs, polluted water, or smoke.  Other causes may be due to birth defects, serious internal diseases, and allergic reactions.
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Laboratory tests, including blood cell counts, conjunctival scrapings and cultures, may be needed to help determine the cause and an effective treatment.  Attempts should be made to prevent further irritation to your petís eyes from such things as contaminated water, soap, dust, sprays, smoke, trauma, etc.
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Corneal Injuries
General Information:
The cornea is the transparent front covering of the eyeball.  It is less than 1 millimeter thick and consists of several complex layers.  It is the most sensitive part of the body and readily reacts to irritants from both outside and inside the eye.
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The corneaís transparency depends on a number of factors that maintain correct water content within the corneal tissues themselves.  Changes in any of these factors through injury or disease may cause the cornea to lose its transparency and become partially or totally cloudy.
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Corneal cloudiness may be caused by trauma, allergic reactions, infections, birth defects, chemicals, and other irritants.
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Treatment depends on the patientís age and the cause and severity of the injury.  Treatment will be based upon your petís individual needs.  Corneal deterioration may progress rapidly after injury, so the eye should be treated as soon as possible.  Pain often accompanies this condition, and medical management will also be directed at eliminating discomfort.
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Disorders of the Nasolacrimal Drainage Apparatus
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General Information:
The nasolacrimal drainage apparatus is the escape route for tears and consists of three parts:
    1.  The puncta: There are four, with one each at the inside corner of each eyelid, just on the inside of
         the lid margins.
    2.  The lacrimal sacs: There are two, one for each eye.  These are dilated or widened areas that
         connect the two ducts that extend from each punctum.  Dacryocystitis is the term used for
         inflammation of the lacrimal sacs.
    3.  The nasolacrimal ducts (tear ducts):  There are two and each extends from each lacrimal sac and
         continues along the muzzle under the lining of the roof of the nose.
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Disorders of the nasolacrimal drainage apparatus include congenital deformities (birth defects), infections, foreign bodies such as plant awns or seeds, and tumors.  The disorders may occur on just one or on both sides.
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General anesthesia may be required for effective treatment.  The patientís activity must be curtailed during the healing period.
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Distichiasis and Trichiasis
General Information:
Distichiasis is an abnormal condition in which extra eyelashes appear along the lid margin(s) where ordinarily they should not grow.  This condition is inherited, but prolonged eye irritation may also cause the unwanted lashes to appear.
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Trichiasis is a similar condition in which the eyelashes grow from normal areas but turn inward and touch the eyeball.
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Both conditions may cause excessive tearing, discomfort and serious injury to the eye.  In some cases, however, the conditions cause no harm or discomfort, and treatment is not required.
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Early eye damage is not readily apparent but may be detected with the aid of special optical instruments.  Thus, treatment can be initiated before serious damage is done.
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Both distichiasis and trichiasis may be present at the same time.
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Various procedures can correct either disorder.  The choice of the treatment will be based on your individual petís needs.  Due to the complex, ongoing nature of distchiasis and trichiasis new irritating eyelashes may appear after the initial corrective procedure.  Therefore, the  procedure may need to be repeated.  One should not become discouraged since correction can be attained, and each additional procedure reduces the likelihood of recurrence.
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Notify your veterinarian if any of the following occur:


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Ectropion
General Information:
Ectropion is the turning out (eversion) of the eyelid.  Besides being unattractive, ectropion can cause irritation because it exposes the sensitive inner lining of the eyelids and eyeballs to irritants.  It also allows drying of the eyeball due to increased tear evaporation.  It may also prevent efficient spreading of the tears during the blink reflex.
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Ectropion may be normal and harmless in some dogs, but abnormal and harmful in others.  Causes include inherited factors, birth defects, and injuries.
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Ectropion is corrected by surgery, with the animal under general ansthesia.
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Entropion
General Information:
Entropion is a rolling in of the eyelids.  It may cause the eyelashes to rub against the sensitive front layer of the eyeball (cornea) and is often uncomfortable or painful.  It can also cause serious eye damage.
Causes include birth defects, injuries and other eye disorders.  Entropion may be permanent or temporary and may occur at any age after the eyes open at around 2 weeks.
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The objective of treatment is to permanently evert or roll the affected lid(s) outward.  Hospitalization and general anesthesia will be required.  Further lid adjustment may occasionally be needed at a later date due to tissue contraction or growth.  "Tacking" is a term used when the lids are temporarily turned outward with the use or sutures.  The sutures remain in for an average of 2-3 weeks.  The procedure is used on very young animals to protect the sensitive front of the eyeball until the lids attain less harmful eyeball contact through natural maturing.  In some instances, a more permanent, surgical repair may be required at a later date on these patients.
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Enucleation (eye removal)
General Information:
Enucleation is the surgical removal of the eyeball.  It is a last-resort treatment for very serious eye diseases or injuries after all other alternatives have been carefully considered.
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Modern surgical techniques allow minimum disfigurement and maximum comfort to the patient.  After the eyeball is removed, the eyelids are sutured permanently closed.  This procedure is an acceptable, humane alternative to destruction of the animal.
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After healing is complete, most animals show only a faint scar and a shallow indentation of the skin where the eyeball was removed.  If your pet has long hair, the area may be hidden by various grooming techniques.  Animals adjust very well to single-eyed vision.
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Your pet will be examined before surgery to determine if there are any medical problems that increase the risk of general anesthesia and surgery.  Laboratory tests and radiographs (x-rays) may be required.
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Epiphora (excessive tearing)
General Information:
Epiphora results in persistent wetness and often staining of the area below the eyes.  This is not only unsightly but may become irritating to your pet, since it creates an excellent bed for bacterial growth.
Causes include allergies, infections, foreign matter, abnormally located eyelashes and adjacent facial hair that rub against the eyeball, defects or diseases of the tear drainage system, birth defects of the eye.
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Glaucoma
General Information:
Glaucoma is a disease in which pressure within the eyeball increases to dangerous levels.  It is one of the most common causes of blindness in dogs and cats.
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The maintenance of normal pressure within the eye depends upon a delicate balance between production and escape of internal eye fluid (aqueous humor).  If fluid flow is blocked, the internal eye pressure may rise to dangerous levels (glaucoma) that can permanently destroy the retina and injure other vital structures of the eye.
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The eyeball may become enlarged if glaucoma persists over a long period of time.
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The causes of glaucoma include blockage of the drainage passage due to birth defects (possibly inherited), inflammatory conditions, injuries tumors, blockage of the pupil, and lens disorders.
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Treatment is to reduce the pressure and relieve pain.  Vision may be permanently destroyed within hours if the internal eye pressure is high enough.  Treatment is complex and may require hospitalization.  Medicine alone often will not control glaucoma over time, and other procedures may be needed to save vision, reduce pain or improve appearance.  If primary (not form injury or infection) glaucoma occurs in one eye, chances are increased that it will occur in the opposite eye.  One should be alert for early signs of glaucoma in the other eye.  The internal eye pressure should be monitored periodically according to your petís needs and response to treatment.
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Notify your veterinarian if any of the following occur:


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Keratitis
General Information:
Keratitis is an inflammation (with or without infection) of the clear front layer of the eyeball (cornea).  It may be a serious threat to vision.
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The cornea has 4 distinct layers and is less than a millimeter thick.  Normally it contains no blood vessels or pigment and is transparent.  Disease or injury may cause cloudiness, pigmentation, vessel ingrowth and ulcerations.
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Causes of keratitis include injuries, irritation, immune or allergic reactions, infections and birth defects.
Keratitis is described according to the corneal layers affected and the shape and nature of the abnormality.  Some types include superficial, interstitial, deep, ulcerative, pigmentary, punctate, dystrophic, allergic, and degenerative keratitis.
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Treatment varies according to type and severity of the keratitis.  Laboratory tests and surgery may be required.  It is important to prevent further irritation to eye(s) from contaminated water, wind, sprays, smoke, and trauma.
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Kertoconjunctivitis Sicca (dry eye)
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General Information:
Dry eye is a disease in which tear production is absent or decreased.  The front layer of the eye (cornea) dries out and becomes painful.  Loss of vision can result.
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Tears are produced from 2 major sources: the tear glands positioned above each eyeball, and the accessory glands distributed throughout the front of the eyes, including the eyelids.
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Disease or destruction of these tear glands may reduce tear production to an unhealthy level.  The exact cause in individual cases may be unknown; however, typical causes include trauma, chemicals, infections, tumors, nerve degeneration and immune reactions.
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Your patience and determination are critical to your petís comfort, since medical attempts to correct the condition may take weeks to months or may never be entirely successful.  Even if normal tear production never returns, you can provide increased comfort to your pet and usually preserve some vision.  Providing eye lubrication during the treatment period is very important, because keeping the eyes moist increases the chances of curing the disease.  If normal tearing is unattainable, then an operation called parotid duct transposition my be performed.  It involves redirecting a salivary duct from the mouth to the eye so that saliva substitutes for tears.  The operation is not without problems and is recommended only after intense effort is made to treat the condition with medicine alone.
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Notify your veterinarian if any of the following occur:


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Nictitans Gland Protrusion (cherry eye)
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General Information:
The third eyelid (membrana nictitans) lies between the eyelids and the eyeball at the inside corner of each eye.  Its purpose is to protect the eye and to help contain and spread tears over the cornea.  The third eyelid also contains tear-producing glands and therefore contributes to the overall lubrication of the eye.
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The gland of the third eyelid lies within the substance of the third eyelid and occasionally protrudes over the free edge of the third eyelid.  As a results, the exposed, sensitive tissue becomes very irritated and inflamed, causing considerable discomfort.  The reddened, swollen tissue resembles a cherry; hence the common name of this condition is "cherry eye."
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Use of medication alone often fails to alleviate the condition.  Surgery is usually required for correction.
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Pannus (chronic superficial keratitis)
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General Information:
Pannus is a progressive, degenerative disease of the transparent front of the eyeball (cornea).  It affects primarily German Shepherds, but may also affect other breeds.  As the disease progresses, blood vessels, pigment and scar tissue become incorporated into the outer layers of the cornea.  If the disease continues, the cornea loses its transparency and blindness may result.
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The cause of pannus is not well understood.  Pannus appears to result from an allergic reaction in which the body does not recognize its own corneal cells and attacks them.  Excessive sun exposure may be one cause, but this has not been proven.
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Pannus tends to occur in certain families; therefore the disease could be inherited.  This is also unproven.
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Treatment usually results in control of the disease rather than a complete cure.  Therefore, a commitment to long-term treatment, possibly for life, is necessary to preserve your petís vision.  Fortunately, in most cases vision can be preserved.  The initial treatment of pannus is often intense, but if the response is good, continued treatment can be made more practical.  Certain cases require surgery which may need to be repeated at various intervals.
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Progressive Retinal Atrophy
General Information:
Progressive retinal atrophy (PRA) is a name given to a broad group of eye diseases of similar character.  It causes no pain or discomfort but leads to permanent blindness.  The word atrophy means wasting away.
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PRA develops after birth, and it has been determined in some breeds to be inherited from both parents.  It affects the retina which lines the inner eye.  The retina contains the light-sensitive rods and cones that change light into energy for transmitting messages to the brain.  The retina is similar to the film in a camera Ė the image or picture is received on it.
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PRA occurs in all breeds of dogs and cats.  It appears earlier in some breeds and can take several years to cause complete blindness.  An early sign of PRA is inability to see in dim light.
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Due to PRAís slow progress, most pets adapt very well to the gradual loss of sight.  Many owners do not realize their pet is becoming blind.  Animals compensate well for blindness, and their other senses are much more acute than those of people.
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There is no treatment available, and complete blindness will eventually result.  PRA is eliminated through selective breeding of animals with normal eyes.
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Ulcerative Keratitis (corneal ulcer)
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General Information:
The cornea is the transparent front layer of the eyeball.  It is less than 1 millimeter thick and consists of several complex layers.  It is the most sensitive part of the body and readily reacts to irritants or stimuli from both outside and inside the eye.
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Ulcerative keratitis is corneal inflammation caused by disruption in one or more layers of the cornea, starting from the outside going inward.  The disruption (ulcer) may be very shallow, similar to a scrape or an abrasion, or it may be very deep, nearly penetrating all the corneal layers.  The deeper the ulcer is, the more vision is threatened.
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Corneal ulcers have many causes, including trauma, infections, inborn weaknesses, and nutritional deficiencies.
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Once a corneal ulcer occurs, rapid deterioration of the cornea may result.
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Corneal ulcers are quite painful, and treatment to reduce discomfort will be given.  Further irritation or damage should be prevented.  Bright light may be an irritant.  Treatment includes use of medicine with or without surgery.  Artificial lenses are also used in selected cases.
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Uveitis
General Information:
Uveitis is inflamation of the iris, ciliary body, and choroid.  These major structures of the eye are very sensitive and perform numerous functions required for vision.
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Uveitis is described in 3 ways: Causes include inflammation, infection, immune-mediated reactions (a complex allergic-type reaction), and injuries.
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Uveitis is painful and can cause blindness.
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The cause determines the treatment used and may range from routine outpatient therapy to intense and complex procedures requiring hospitalization.  Special diagnostic tests are sometimes required.  Specific attention is given to pain control, and any factors that cause further irritation should be eliminated or avoided.  These include wind, dirt, sand, sprays, smoke, and bright light.
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Notify your veterinarian if any of the following occur: