SECTION 13 Diseases of the Eye

Section Editor: Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

Anterior Uveitis

Cataracts

Chorioretinitis and Optic Neuritis

Collie Eye Anomaly

Conjunctivitis

Corneal Ulceration

Distichiasis and Ectopic Cilia

Ectropion

Entropion

Eyelid Tumors

Feline Corneal Sequestration

Feline Eosinophilic Keratitis

Feline Herpesvirus Keratoconjunctivitis

Glaucoma in Cats

Glaucoma in Dogs

Horner’s Syndrome

Hypertensive Retinopathy

Hyphema

Intraocular Tumors

Iridociliary Cysts

Iris Melanosis of Cats

Keratoconjunctivitis Sicca (Dry Eye)

Lens Luxation and Subluxation

Lipid Keratopathy

Orbital Cellulitis and Abscessation

Orbital Tumors

Pannus

Persistent Corneal Erosions

Pigmentary Keratitis

Progressive Retinal Atrophy

Prolapse of the Gland of the Third Eyelid

Proptosis of the Eye

Retinal Detachment

Retinal Dysplasia

Sudden Acquired Retinal Degeneration

Taurine Retinopathy

Anterior Uveitis

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment involves administering medications for the eye problem and for any underlying causes. Typical eye medications include topical anti-inflammatory drugs (usually steroids), pupil dilators/pain relievers (such as atropine), and sometimes antibiotics and anti-glaucoma drugs. The severity of the inflammation often dictates how frequent and intense the therapy must be.

Once an underlying cause is determined, appropriate treatment is started for that condition. Examples include antibiotics, antifungal agents, and drugs for hypertension and blood disorders. Oral anti-inflammatory agents may also be used, but the administration of steroids is often delayed until infectious diseases are ruled out.

Removal of the eye may be recommended in cases of suspected intraocular tumors, blind eyes that remain painful, eyes with unresponsive glaucoma, or concern that an infection may persist in the eye and spread to other parts of the body (especially certain fungal infections).

Follow-up Care

Some cases of uveitis respond quickly to medications and resolve within days. Other cases of uveitis are more stubborn and require months of therapy. Prolonged therapy is often needed in cats with chronic uveitis, in dogs with fungal infections, in eyes with severe inflammation, and when the underlying cause is difficult to treat.

Recheck visits are done to assess response to treatment and to monitor for complications, such as glaucoma. Certain laboratory tests may also be repeated to monitor for side effects associated with the oral drugs used to treat uveitis.

Report any worsening of signs, particularly increased pain (squinting) or cloudiness, to your veterinarian immediately.

Prognosis

Whether uveitis will successfully resolve often depends on the underlying cause, the severity of the inflammation, and the diligence of the treatments. Many cases resolve with adequate therapy, but the animal must be monitored closely for recurrence of the inflammation as medications are tapered and stopped. Some cases of uveitis do not respond well and result in blindness or loss of the eye. Chronic uveitis in cats may require prolonged therapy (months to years).

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Cataracts

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

A cataract is an opacity within the lens of the eye. Cataracts can be classified by their severity, age at onset, or underlying cause. Incipient cataracts are the mildest type, involve only a small portion of the lens, and do not affect vision. Immature cataracts affect 25-90% of the lens, may be severe enough to affect vision, and may be visible to owners. When the lens is completely opaque, a mature cataract is present, and vision is substantially decreased. Some cataracts shrink a little over time and become wrinkled. These hypermature cataracts may cause inflammation within the eye.

Based on the age at onset, a cataract may be described as congenital (present at birth), juvenile (onset at a few months to several years of age), adult, or senile (older animals). Cataracts are less common in cats than in dogs.

Causes

Congenital cataracts may arise from abnormal development of the lens or other ocular defects. Inherited cataracts are the most common type in dogs; they affect more than 40 different breeds and can arise at any age.

Other causes of cataracts include diabetes mellitus (sugar diabetes) in dogs, nutritional deficiencies (especially in the newborn), trauma to the eye, inflammation within the eye (such as uveitis), low blood calcium (rare), retinal degeneration, radiation therapy, and exposure to certain toxins or drugs (rare).

As they grow old, all animals develop a hardening of the center of the lens, which turns the lens a milky, gray-white color. This aging change is called nuclear or lenticular sclerosis. It is not the same as a cataract and is rarely treated.

Clinical Signs

Cataracts are often quite cloudy before vision is affected. Cloudiness in the eye may be detected first. Redness may also occur if the eye is inflamed. If the dog has sugar diabetes, then increased thirst and urination may be noted.

Diagnostic Tests

A complete eye examination is needed to confirm the diagnosis and may involve glaucoma testing and dilation of the pupil. Laboratory tests are usually performed to look for underlying causes. Simple lenticular sclerosis must also be ruled out.

TREATMENT AND FOLLOW-UP

Treatment Options

To date, there is no effective medical therapy for cataracts. Products available on the Internet have had minimal beneficial effects. Cataracts that are small and do not affect vision may require no treatment. Not all cataracts progress, so monitoring may be the only initial recommendation.

For cataracts that are progressing and have reached the immature stage, surgical removal of the lens remains the most effective treatment. Not all eyes are candidates for surgery, however. In order for the eye to be operable, it must be free of inflammation, have a healthy retina, and have no evidence of glaucoma. In addition, any sugar diabetes must be well regulated prior to surgery, and the animal must be able to withstand general anesthesia.

Cataracts that are secondary to uveitis or retinal degeneration, associated with retinal detachments or other ocular defects, or complicated by other eye diseases (such as corneal edema, glaucoma, or tumors) are not often operable.

Your pet may be referred to a veterinary ophthalmologist to assess the cataract and determine what treatment options are available. If the eye is a potential candidate for surgery, two preoperative tests are usually recommended: an electroretinogram (ERG) to measure retinal function and an ultrasound of the eye to ensure that no retinal detachments are present. Anti-inflammatory medications may be given prior to surgery.

Most operable cataracts can be removed via phacofragmentation surgery. This is not laser surgery. It involves use of ultrasound to shatter and remove lens material through a small incision. If both eyes are affected and otherwise healthy, they are often operated at the same time, to avoid two general anesthetic procedures. If the lens bag (capsule) that is left behind is healthy, then an intraocular lens implant (IOL) may be inserted to improve close-up vision.

Follow-up Care

Postoperatively, medications must be administered several times daily for weeks to months, and numerous recheck visits are needed. Close monitoring for complications, such as postoperative uveitis, glaucoma, and retinal detachments, is important. Often the animal must wear an Elizabethan collar for 3-4 weeks while the incision is healing.

Prognosis

For uncomplicated cataracts in healthy eyes, the success rate of cataract surgery is quite high (85-90%). Success rates are lower in eyes that have been inflamed or affected by glaucoma and for cataracts that are hypermature. Cataract surgery is considered an elective surgery, because most animals do quite well with diminished or no vision.

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Chorioretinitis and Optic Neuritis

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Inflammation of the tissues of the back of the eye (choroid, retina) is called chorioretinitis. The choroid is part of the uvea of the eye, so inflammation of the choroid may be called posterior uveitis. Involvement of the nerve leading from the eye to the brain is called optic neuritis. These conditions may occur alone or together and are inherently serious because they affect vision.

Causes

With the exception of trauma to the eye, these conditions are usually manifestations of a systemic or generalized problem. The choroid and retina are commonly affected by other diseases within the body, and optic neuritis may arise with certain disorders of the brain. Numerous causes must be considered:

• More than 25 different infections can cause this inflammation, including fungal, tick-borne, bacterial, viral, protozoal, and parasitic infections. Some types occur more often in dogs, whereas others are more common in cats.

• In rare instances, the immune system may attack the uvea, and other parts of the body may also be affected.

• Tumors may arise within the eye or metastasize to the eye from elsewhere in the body.

• Hypertension (high blood pressure), anemia, kidney disease, sugar diabetes, elevated blood protein levels, and other blood disorders may be causes.

Clinical Signs

Inflammation confined to the back of the eye may not be visible and may not be discovered until the animal is examined for other signs of illness. Inflammation that also affects the front of the eye can cause the eye to be red, cloudy, and painful (squinting). Vision may be affected, resulting in pupils of different sizes. If both eyes are inflamed, the animal may act blind. The onset of blindness can be quite sudden (within days).

Diagnostic Tests

Diagnosis of these conditions can be difficult without specialized instruments to examine the back of the eye. If the diagnosis cannot be confirmed, your veterinarian may refer your pet to a veterinary ophthalmologist or neurologist for further evaluation. A complete physical examination is usually performed to search for any other changes that may signify the presence of a generalized (systemic) problem.

Laboratory tests are frequently done to search for infections and underlying causes. Chest and abdominal x-rays and an abdominal ultrasound are sometimes recommended. If hypertension is suspected, blood pressure can be measured. In eyes that are cloudy and cannot be examined well, an ultrasound may be performed. If a brain disorder is suspected, computed tomography (CT scan) or magnetic resonance imaging and a spinal tap may be recommended. The cause of chorioretinitis and/or optic neuritis can be difficult to find and may require numerous tests.

TREATMENT AND FOLLOW-UP

Treatment Options

Treatment involves administering medications for the eye problem and for any underlying causes. Medications applied to the eye do not reach the retina and choroid but topical anti-inflammatory drugs (usually steroids), pupil dilators/pain relievers (such as atropine), and antibiotics may be used for inflammation in the front part of the eye.

Once an underlying cause is determined, appropriate treatment is started for that condition. Examples include antibiotics, anti-fungal agents, drugs for hypertension and blood disorders, and chemotherapy for certain tumors. Oral anti-inflammatory agents can reach the retina, choroid, optic nerve, and brain, but the administration of steroids is often delayed until infectious diseases are ruled out and a specific cause is determined.

Removal of the eye may be recommended in cases of suspected intraocular tumors, blind eyes that remain painful, eyes that develop unresponsive glaucoma, or concern that an infection may persist in the eye and spread to other parts of the body (especially certain fungal infections).

Follow-up Care

Chorioretinitis and optic neuritis often indicate the presence of a serious underlying disease. If treatable, these diseases usually require prolonged therapy (months), periodic recheck visits, and careful monitoring. Certain laboratory tests may be repeated to monitor for side effects associated with the oral drugs used to treat these conditions.

Report any worsening of signs, particularly the onset of pain (squinting) or decreased vision, to your veterinarian immediately.

Prognosis

Whether chorioretinitis or optic neuritis will resolve often depends on the underlying cause, the severity of the inflammation, and the diligence of the treatments. Many cases improve with adequate therapy, but permanent scarring within the retina may result in blindness. Some forms of optic neuritis improve with treatment but are not cured, so therapy must be continued for the life of the animal. Some of the causes of these conditions are life-threatening.

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Collie Eye Anomaly

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Collie eye anomaly (CEA) is abnormal development of the retina and the sclera (the white, firm, outer coating of the eyeball). CEA affects both eyes and occurs most often in rough and smooth collies. It is also found in the Shetland sheepdog, Australian shepherd, Lancashire heeler, and border collie.

Causes

CEA is inherited as an autosomal recessive trait. Dogs that inherit an abnormal gene from each parent (homozygous) will develop CEA. Dogs that inherit an abnormal gene from only one parent (heterozygous) will be carriers of the disease.

Clinical Signs

The following lesions are components of CEA:

• Choroidal hypoplasia is the most common lesion of CEA and represents underdevelopment of a portion of the retina and its background layer (the choroid). Lesions of choroidal hypoplasia may range from small to large. They do not often affect vision.

• A coloboma is a pit or hole in the back of the eye. It may affect the optic nerve as it leaves the retina or some nearby area. Small colobomas are not usually associated with vision abnormalities, but large colobomas may cause decreased vision and predispose the retina to detachment.

• The retinal vessels may be tortuous in some dogs, meaning that they twist and turn in an abnormal fashion. These vessel changes do not affect vision unless they predispose the eye to retinal hemorrhages.

• Retinal detachments can occur and may be partial or complete. Complete detachment results in total blindness, often by 6-12 months of age.

• Retinal hemorrhages may occur spontaneously, or they may be associated with retinal detachment.

Diagnostic Tests

The diagnosis of CEA is made by examination of the retina using an ophthalmoscope. Since most lesions of CEA are present at birth, CEA can be seen in puppies as early as 6 weeks of age. Retinal examination is facilitated by the application of drops to dilate the pupils. It is common for entire litters of puppies to be examined at 6-7 weeks by a veterinary ophthalmologist.

Examination at an early age helps to determine which puppies may potentially be used for breeding in the future and which puppies may develop vision abnormalities. Early examination is also important to identify all affected puppies. Puppies with only mild choroidal hypoplasia may be hard to recognize by 10-12 weeks of age, because mild hypoplasia lesions may fill in with pigment and disappear from view. Although these puppies look normal (and are called go normals), they are actually affected with CEA.

A genetic test for CEA has also been developed that can identify affected, carrier, and normal dogs. The test is performed on a blood sample and is available from OptiGen (www.optigen.com).

TREATMENT AND FOLLOW-UP

Treatment Options

No treatment exists for CEA. To date, no effective treatment is available to prevent the retinal detachments associated with this condition. Laser therapy may be tried for partial retinal detachments, if they are discovered early. To eliminate CEA from collies and other affected breeds, it is recommended that only normal animals be used for breeding. Because CEA is so widespread in the collie breed, homozygous normal dogs are hard to find. In collies, it is common for dogs with only choroidal hypoplasia to be used for breeding. Dogs with only the mildest form of the disease may still produce puppies with more severe lesions, if they are bred to another affected or carrier dog.

Follow-up Care

With the exception of the development of a retinal detachment, CEA is not a progressive disease. Puppies at risk for retinal detachments may be monitored periodically. Notify your veterinarian if any decrease in vision is noted.

Prognosis

Prognosis for puppies with choroidal hypoplasia or mild colobomas is good, because these lesions do not usually affect vision. Vision may be affected by larger colobomas. Retinal detachment invariably results in blindness in the affected eye. Retinal detachment can occur in one or both eyes.

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Conjunctivitis

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Conjunctivitis is inflammation of the tissues lining or covering the eyelids and eyeball.

Causes

Numerous factors can lead to conjunctivitis, including infection by bacteria or viruses (especially herpesvirus in cats), irritants, and trauma. Irritants can include chemicals, smoke, dust, soap, foreign bodies, abnormal hair, and many others. Young dogs (less than 1 year of age) may develop follicular conjunctivitis, which appears to be an excessive immune response to environmental irritants.

Certain forms of conjunctivitis may develop with allergies or accompany immune disorders. Conjunctivitis often occurs in eyes with dry eye (keratoconjunctivitis sicca). It can occur in association with many systemic or generalized illnesses, such as upper respiratory tract infections and generalized viral or bacterial infections. Rarely, parasites, fungal infections, and tumors of ocular tissues can cause conjunctivitis.

Clinical Signs

Redness of the conjunctiva is a common sign. Ocular discharge often develops and may be watery, mucoid (gelatinous, gray), or pus-like (thick, yellow-green). Swelling of the conjunctiva may occur in some cases. Follicular conjunctivitis in dogs receives its name from the small white swellings (follicles) that develop on the third eyelid and conjunctiva. Some forms of conjunctival inflammation (such as eosinophilic conjunctivitis in cats) can cause small pink growths to develop on the conjunctiva. With widespread or severe conjunctivitis, inflammation of the eyelids (blepharitis) or of the cornea (keratitis) may also occur.

Most eyes with mild conjunctivitis are not painful. Eyes with conjunctivitis associated with trauma, chemical burns, corneal ulceration, or foreign bodies may be painful (indicated by squinting, pawing, and so on).

Diagnostic Tests

Conjunctivitis must be differentiated from other causes of a red eye, including glaucoma, corneal ulceration, scleritis (inflammation of the deeper white tissue covering the eyeball), and uveitis (inflammation inside the eye). Other conditions, such as skin diseases and tumors of the eyelids that can affect the conjunctiva secondarily, may also be involved. A thorough eye examination with a tear test, fluorescein staining for a corneal ulcer, and glaucoma testing (intraocular pressure measurement) is often performed to rule out some of these other conditions.

To identify potential causes, further testing may include a conjunctival scraping and examination of the cells under the microscope (cytology), submission of a bacterial culture, or special assays for viruses. Biopsies are sometimes done in severe, unusual, or unresponsive cases.

TREATMENT AND FOLLOW-UP

Treatment Options

Specific treatment is directed at the underlying cause.

• For example, if irritants are thought to be the cause, then removal of the source of irritation is important. Local foreign bodies or exposure to chemicals is usually treated with flushing of the eye.

• Antibiotics are given for bacterial infections, and antiviral medications may be given for viral infections. These medications may be administered topically and orally (systemically).

• Conjunctivitis associated with dry eye often improves with therapy for that condition.

• Topical antihistamines and steroids are often used when conjunctivitis occurs in association with allergies or is thought to be an immune disease.

• The rare parasitic infestations are treated by removal of the parasite and ant-inflammatory medications.

Symptomatic treatment for conjunctivitis of unknown or uncertain origin may involve the administration of a topical antibiotic or steroid preparation, installation of soothing lubricant agents, and possibly the use of other anti-inflammatory drugs.

Follow-up Care

Some forms of conjunctivitis respond very quickly, whereas others are stubborn and require prolonged therapy. Recheck visits are frequently needed to evaluate the eye’s response to treatment and to decide whether further diagnostic tests or other therapies are needed. Recheck visits also allow other associated problems (such as corneal ulceration or blepharitis) to be assessed.

Any eye with conjunctivitis that becomes painful (squinting, pawing at the eye) warrants re-examination as soon as possible; in the meantime, all steroid medications being administered are stopped.

Prognosis

Many forms of conjunctivitis, including those caused by one-time exposure to irritants, trauma, or corneal ulcers, resolve completely. Other forms of conjunctivitis can recur intermittently or become chronic. Examples of these include herpesvirus or eosinophilic conjunctivitis in cats and conjunctivitis associated with dry eye or allergic skin disease.

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Corneal Ulceration

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

A corneal ulcer occurs when the protective surface layer of the cornea is lost. The deeper layers of the cornea are exposed and become prone to infection and injury. These deeper layers contain many nerves, and irritation of these nerves is very painful. Corneal ulcers range from superficial abrasions and small circular lesions to deep craters that may perforate. Ulcers may be complicated by secondary bacterial infections and by severe inflammation of the eye.

Causes

Many different causes exist, including trauma (such as cat scratches or foreign bodies), abnormalities of the eyelids (entropion, extra or abnormal eyelashes), decreased blinking (during sedation or general anesthesia, neurologic problems), and exposure to irritants (chemicals, soaps, heat or flame). Infections with bacteria, viruses, or fungal agents can cause ulcers. The presence of dry eyes or calcium infiltrates and edema (water retention) in the cornea can also predispose to ulceration.

Dogs with short, flat faces and prominent eyes are very prone to corneal ulcers, because their eyes are large and protrude beyond the eyelids. These dogs also have poor sensation (feeling) in the central cornea and blink less often than other dogs.

Clinical Signs

Pain is a hallmark sign of corneal injuries and ulceration. It is manifested by tearing, squinting, blinking, and sometimes pawing at the eye. The animal may also be quiet and withdrawn.

The eye is usually red. Thick discharge may develop with infection. The cornea may be cloudy or have visible irregularities. Other signs, such as swelling of the eyelids, inward rolling of the eyelid, protrusion of the third eyelid, or bruising around the head, may occur depending on the cause. Signs of upper respiratory tract infection may be noted in cases of herpesvirus infection in cats or distemper virus infection in dogs.

Diagnostic Tests

The presence of a corneal ulcer is confirmed by close examination and fluorescein staining of the cornea. Installation of a local anesthetic drop to numb the eye may be needed prior to examination. Other ocular testing, such as a Schirmer tear test, testing of reflexes, examination of the eyelids and interior of the eye, and glaucoma testing, may also be indicated. If a bacterial infection is suspected, a culture of the eye may be submitted.

TREATMENT AND FOLLOW-UP

Treatment Options

Many ulcers can be treated on an outpatient basis, but hospitalization may be recommended for severe ulcers. Treatment can involve medications, surgery, and other measures, depending on the type and severity of the ulcer. Medications are applied to all ulcers:

• Topical antibiotics are administered to treat active infections and/or to prevent infections. If the ulcer is deep and there is concern about infection within the eye, then oral or injectable antibiotics may also be given.

• Topical atropine (pupil dilator) or other pain medications (nalbuphine, morphine) may be given, as needed.

• Topical and/or oral antiviral and antifungal medications are given for those infections.

• Oral nonsteroidal anti-inflammatory drugs may be considered for marked inflammation and discomfort, especially in dogs.

Ancillary measures include application of an Elizabethan collar to prevent self-trauma, application of soft contact bandage lenses, placement of a third eyelid flap to protect the cornea, and administration of the pet’s own serum (used mainly for soft, melting ulcers). Surgical correction of any underlying causes, such as entropion correction or removal of foreign bodies or abnormal lashes, is also beneficial.

If the ulcer is deep enough to weaken the cornea, then supportive surgical techniques are often performed. These include various types of grafting techniques that use either conjunctival tissue from the animal’s eye or harvested tissue from another animal. Small, deep lesions can sometimes be directly closed by suturing the edges together.

Follow-up Care

Recheck visits are needed to assess healing and response to treatment. Visit frequency can range from every 24-48 hours to every 7-14 days, depending on the severity. Fluorescein staining of the cornea is done at most visits to highlight the ulcer and to determine when it has healed.

Prognosis

Most superficial ulcers and abrasions heal quickly, with minimal scarring. Deep ulcers and ulcers that are infected are more difficult to treat, and secondary changes such as inflammation within the eye or scarring and pigmentation of the cornea can decrease vision. Certain bacteria produce substances that can melt the cornea, sometimes resulting in perforations and loss of vision and the eye. Ulcers that require surgical grafting often must be treated and monitored diligently for several weeks.

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Distichiasis and Ectopic Cilia

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Normal eyelashes develop from hair follicles on the skin surface of the eyelid. Distichia and ectopic cilia are eyelashes that grow from small glands in the middle layer of the eyelid. Distichia grow out the duct of the gland and point downward or upward from the smooth edge of the eyelid. These cilia may brush against the cornea as the lids open and close. Ectopic cilia exit from the conjunctival or inner surface of the lid and point directly at the cornea. Ectopic cilia most often develop on the central upper eyelid and may occur alone or in combination with distichia. Ectopic cilia may arise in just one eye, but it is common for distichia to be found in both eyes.

Causes

Distichiasis may be inherited. It is common in certain breeds of dogs, such as the American cocker spaniel, shih tzu, Bedlington terrier, boxer, Weimaraner, Shetland sheepdog, collie, Pekingese, and others. Purebred dogs are affected more often than mixed-breed dogs and cats. Ectopic cilia are less common but may be found in all types of dogs, usually before 1 year of age.

Clinical Signs

Signs associated with distichiasis often depend on the number and character of the lashes present. American cocker spaniels often have numerous distichia, but they are short and fine and often cause no clinical signs. In other dogs, watery tearing, increased mucus production, blinking or squinting, or conjunctivitis may be noted. Corneal ulcerations may occur in some dogs.

Ectopic cilia often cause corneal ulcers, marked squinting, and pain. Signs may improve for awhile if the conjunctiva grows over the eyelash, but invariably they return when the cilia grows longer and becomes exposed again. The resulting corneal ulcer does not respond well to medical therapy.

Diagnostic Tests

Distichia can often be seen with the naked eye and a light beam focused on the eyelid, but ectopic cilia can be very difficult to see. Magnification is often needed to locate ectopic cilia. The cornea is often stained with fluorescein to determine the presence of an ulcer. The eyelids and surface of the eye are also examined for other defects.

TREATMENT AND FOLLOW-UP

Treatment Options

No treatment of distichiasis is needed in dogs that are asymptomatic (including most American cocker spaniels). If only a few distichia or only minor signs are present, then topical lubricant ointments may be used to coat the cilia in oil and protect the cornea. If signs resolve, then this therapy may be continued indefinitely. Temporary plucking of the eyelashes is not usually performed, because they invariably grow back.

Multiple distichia are often treated with cryotherapy, which is the application of a freezing agent to the underside of the eyelid, over the affected gland. Affected glands may also be cauterized, but the heat generated by cautery often damages surrounding tissues more than freezing does. Surgery to remove the hairs is not often performed unless only one or two clusters are present.

Ectopic cilia are best treated by surgical removal of the cilia and the associated eyelid gland. Because these lashes are so small, surgery may be performed under an operating microscope. It is important to remove these cilia as soon as possible, so that the cornea is no longer irritated and pain is relieved.

Follow-up Care

Following distichia surgery, a topical antibiotic or lubricant may be applied to protect the cornea, because eyelid swelling is common for several days. An Elizabethan collar may also be applied to prevent self-trauma. Dark eyelid margins may turn pink after they are treated with cryotherapy, but the black color typically returns in 6-8 weeks.

After surgery for ectopic cilia, topical antibiotics and pain relievers may be used for corneal ulcers, and an Elizabethan collar may be applied until the ulcer heals. Dogs are periodically monitored postoperatively until the corneal ulcer and surgery site have healed.

Prognosis

No single procedure is effective for removing all distichia, because hair follicles are very difficult to kill. Some distichia can be expected to persist or return. In addition, more distichia may grow in new locations over the course of months to years. Periodic monitoring for regrowth is warranted, and repeated treatments may be needed.

Many dogs with ectopic cilia are cured with one surgery, if the entire hair follicle and associated glands are removed completely. Any recurrence of clinical signs (especially pain and squinting) requires re-examination for regrowth or eruption of new cilia.

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Ectropion

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Ectropion is outward rolling of the eyelid and usually involves the central part of the lower eyelid. It may also affect the upper lid. It occurs predominantly in the dog.

Causes

Ectropion may be inherited and may develop early in the American cocker spaniel, basset hound, bloodhound, Clumber spaniel, Great Dane, Newfoundland, mastiff, Saint Bernard, boxer, and other breeds. The Saint Bernard often has ectropion of the central eyelids, entropion of the outer portion of the eyelids, and excessive lid length, giving the opening of their eyes a “pagoda” or “diamond” shape. Individuals in other breeds may have a similar eyelid conformation.

Acquired ectropion may occur after eyelid trauma (especially lacerations or bite wounds) or eyelid surgery (such as overzealous entropion repair or removal of large lid tumors). Acquired ectropion may also develop in older dogs from decreased muscle tone of the eyelids and may be noted temporarily in hunting dogs when they become tired. Ectropion may also occur with paralysis of the seventh cranial nerve, which activates the eyelid muscles.

Clinical Signs

Many dogs have no clinical signs except for increased visibility of the conjunctiva of the lower eyelid. If the eyelid does not protect the nearby cornea or if ectropion is combined with entropion, then signs of corneal inflammation or ulceration (squinting, discharge, redness) may occur. Debris sometimes collects in the gap between the affected portion of the eyelid and the cornea and may be irritating to the eye.

Diagnostic Tests

Diagnosis is usually made by close examination of the eyelids. The eyelids may also be assessed for entropion, before and after local anesthetic drops are applied. The cornea is often stained with fluorescein to determine whether an ulcer is present.

TREATMENT AND FOLLOW-UP

Treatment Options

Dogs with minimal clinical signs may be treated conservatively by flushing debris from the eye with eye-irrigating solutions and applying a protective ophthalmic lubricant (usually an ointment or gel).

Surgical treatment is usually reserved for those cases with corneal irritation or inflammation, persistent conjunctivitis, or concurrent entropion. A variety of surgical procedures have been developed to correct ectropion, including simple wedge resection of the affected area. More complicated procedures are indicated if entropion and/or excessive lid length are also present.

Follow-up Care

For dogs treated conservatively with medical therapy, periodic rechecks may be indicated to monitor for ocular inflammation. Following surgery, it is common for an Elizabethan collar to be used. Topical antibiotics may also be applied to the eye. Sutures are usually removed in 10-14 days.

Prognosis

Simple ectropion may cause very few problems throughout the lifetime of the dog. Most forms of symptomatic ectropion are helped considerably by surgery.

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Entropion

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Entropion is inward rolling of the eyelid and may involve part or all of one or more eyelids. Entropion may be inherited and develop soon after birth, or it may be acquired.

Causes

Inherited entropion occurs in many different breeds of dogs, including the mastiff, American bulldog, Chinese shar-pei, Great Dane, Doberman pinscher, Labrador retriever, Rottweiler, Saint Bernard, boxer, and others. Because of their excessive facial folds, entropion may develop in shar-pei puppies soon after their eyelids open. In other breeds, the condition becomes obvious over several weeks to months.

Acquired entropion may develop following inflammation, trauma, or chronic eye pain. Acquired entropion is more common in the cat and may arise after ocular infection with feline herpes-virus. Some forms of eye pain cause spastic entropion, which often resolves when the pain subsides.

Clinical Signs

Clinical signs are quite variable and may include mild tearing, squinting and blinking, and production of large amounts of thick discharge. Some animals find it hard to keep their eyes open and may paw or rub at the eyes. The eye may be red, and the cornea may be ulcerated, inflamed, and cloudy. In shar-pei puppies, the eyes may barely be visible.

Diagnostic Tests

Entropion can usually be diagnosed by close examination of the eyelids, before and after local anesthetic drops are applied to the eye. The cornea may be stained with fluorescein to determine whether an ulcer is present.

TREATMENT AND FOLLOW-UP

Treatment Options

Temporary tacking can be performed for entropion in very young puppies. Sutures or staples are placed in the skin above and/or below the eyelids and pulled tight enough to cause the eyelids to roll out. This procedure allows time for the puppy to grow into the facial skin and may prevent the need for permanent entropion surgery. Temporary tacking is also occasionally used for spastic entropion and in animals that cannot undergo general anesthesia.

Spastic entropion usually resolves once the underlying problem has been corrected. Ocular ointments and a soft contact lens may be applied to protect the cornea until the problem resolves.

Most other cases of entropion require permanent corrective surgery. Simple entropion is often corrected by making parallel elliptical incisions in the skin of the affected portion of lid. The skin between the incisions is removed, and when the defect is sutured closed, the eyelid rolls outward. Other surgical techniques may be used if entropion affects the inner or outer corners of the lids or is accompanied by excessive lid length, ectropion, or other defects. In Chinese shar-pei and chow chow dogs that have persistent, excessive skin folds of the forehead, a permanent brow-tacking procedure may be considered after the dog is fully grown.

Follow-up Care

Temporary tacking sutures are sometimes removed by the mother dog as she cleans the puppies’ faces, or they may fall out on their own. If the sutures are retained, they may be removed in 2-3 weeks.

Following permanent corrective surgery, an Elizabethan collar is often applied to prevent trauma to the suture line. Topical antibiotics may also be applied to both eyes, and sutures are usually removed in 10-14 days.

Prognosis

Simple entropion is often corrected with one surgery, and clinical signs usually resolve quickly. Complicated entropion may require more than one surgery or may be treated with staged surgeries, with two techniques performed several weeks or months apart.

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Eyelid Tumors

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Eyelid tumors are growths that occur within or near the eyelids. Most eyelid tumors in the dog are benign, whereas most in the cat are malignant. Older animals are affected most often. The growth rate of eyelid tumors ranges from very slow to very rapid.

Causes

Many eyelid tumors arise from the cells or tissues within the eyelid, but some originate in other locations and spread to the eye or invade the eyelid from adjacent structures.

In the dog, the most common tumor types are the sebaceous adenoma and the papilloma. Tumors that occur in both dogs and cats include the melanoma, mast cell tumor, basal cell carcinoma, squamous cell carcinoma, fibrosarcoma, lymphoma, and others. In most cases, it is not known why these tumors develop.

Clinical Signs

A mass is visible at the edge or within the eyelid. It may be smooth, irregular, nodular, or ulcerated. The color of these masses is quite variable. The eyelid may be deformed and inflamed. Conjunctivitis, ocular discharge, and corneal ulceration may also occur. Most tumors are not painful unless they cause ulceration, in which case the animal may paw or rub the eye and squinting may be noted.

Diagnostic Tests

The presence of a tumor can usually be determined by close examination of the eyelid and eye. Aspiration and cytology of larger masses may provide a tentative diagnosis as to the type of tumor present, but usually a definitive diagnosis requires biopsy and pathologic examination. Other tests may be performed to search for tumors elsewhere in the body if the eyelid tumor is suspected to be malignant or to have originated in another location. Preoperative laboratory tests and chest x-rays may also be recommended prior to anesthesia and surgery.

TREATMENT AND FOLLOW-UP

Treatment Options

Small, benign eyelid tumors can often be removed by a full-thickness resection, which involves taking out a wedge of the eyelid that includes the tumor. The eyelid is then sutured back together. Occasionally, these small tumors are removed with a laser and the defect is not sutured. Larger tumors require more involved surgeries, with formation of a new eyelid margin.

Other treatments that may be tried for particular types of tumors include cryotherapy (freezing), chemotherapy (especially for lymphoma and metastatic tumors), and radiation therapy. In severe cases in which the tumor is malignant and invading the eye or the tissues immediately around the eye, surgery to remove the eye and all affected tissues may be necessary.

Follow-up Care

Following surgery, it is common for the patient to be sent home with an Elizabethan collar in place to keep the animal from bothering the sutures. Topical antibiotics may be administered to the eye. The sutures are usually removed in 10-14 days. Signs of postoperative problems include squinting, tearing, and increased ocular discharge; if any of these signs occur, immediately notify your veterinarian.

Prognosis

Benign tumors that are completely removed are usually cured by surgery. Prognosis is particularly good when the tumors are still small at the time of surgery and the eyelid margin can be reformed as normally as possible. Following extensive surgery to remove large tumors, it may be necessary to monitor for growth of hairs that rub on the cornea and for corneal inflammation.

Malignant tumors often recur at the surgery site and may spread to other areas of the body. Following removal of these tumors, additional treatment and monitoring are usually needed. The long-term prognosis with many of the malignant tumors is poor.

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Feline Corneal Sequestration

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

A corneal sequestrum is an area of dead tissue that arises following some sort of injury or irritation of the cornea. The reasons why a focal area of the cornea dies and becomes discolored are not well understood. The sequestrum appears as a dark brown, almost black spot.

Corneal sequestra can occur in any age of cat, but they usually develop in adult cats (average age, 5.5 years). Persian, Himalayan, British colorpoint, Burmese, Siamese, and American domestic shorthair cats appear to be predisposed. The lesion can occur in one (most commonly) or both eyes. Corneal sequestration has also been called corneal nigrum, corneal mummification, and necrotizing keratitis.

Causes

Numerous sources of irritation may result in a sequestrum, including prior corneal ulceration, entropion (in-rolling of the eyelids), abnormal eyelashes or hair rubbing on the eyes, chronic conjunctivitis, chronic exposure of the cornea, and dry eye from poor tear production. Feline herpesvirus (FHV) infection has also been incriminated as a contributing factor in this disease.

Clinical Signs

A round to oval, black spot develops in the cornea, often near the center. The spot looks very out of place and can be mistaken for a foreign body. The surrounding cornea may be red and cloudy. In some cats, the sequestrum causes no pain. If corneal ulceration is present, the eye may be painful, and the animal may exhibit squinting, tearing, and redness. Although they are rare, severe ulceration and corneal perforation may occur.

Diagnostic Tests

Diagnosis can usually be made by close examination of the cornea, sometimes with magnification. A complete ocular examination often involves tear testing, fluorescein staining of the cornea, and a thorough search for underlying causes. In some cases, cell samples may be submitted for FHV testing. Other causes of dark spots in the cornea, such as foreign bodies and melanoma tumors, must be ruled out.

TREATMENT AND FOLLOW-UP

Treatment Options

For the corneal sequestrum, two main treatment options exist:

• Medical therapy may be tried in cats that do not exhibit pain, especially if the sequestrum is close to the surface of the cornea. Over time, the cornea attempts to reject this dead tissue, and the sequestrum may fall off on its own. This process can be quite slow and may take many months (average, 11 months). The medications used include topical antibiotics, protective lubricants, and sometimes topical or oral antiviral agents.

• Surgery to remove the sequestrum is often chosen for cats that are in pain. Several techniques are available, depending on the size and depth of the lesion. Most involve removal of a portion of the cornea (keratectomy). Because some of these surgical procedures require magnification, such as an operating microscope, your cat may be referred to a veterinary ophthalmologist for the procedure. Healing after simple keratectomy is usually rapid (7-21 days), but it may take a few weeks if a grafting procedure was needed. Postoperative medications may include topical antibiotics, lubricants, pain medications, and antiviral agents.

Any underlying problems must also be addressed. Medications may be started to treat dry eye, FHV infection, or corneal ulcerations. Surgery may be needed to correct entropion or other eyelid problems.

Follow-up Care

Recheck examinations are often performed every 3-4 weeks if medical therapy is tried. Rechecks may be scheduled more frequently if the cornea is ulcerated and inflamed. Examinations often involve fluorescein staining of the cornea and monitoring of the opposite eye.

When surgery is performed, postoperative examinations are usually done every 7-14 days until the cornea is healed. If the sequestrum was quite deep and corneal grafting was required after its removal, then recheck visits may be needed for several weeks.

Prognosis

Corneal sequestra recur in 10-20% of affected eyes and can develop at a later date in the opposite eye. The reasons for recurrence are not well defined but may include failure to adequately address contributing factors; inability to remove the entire sequestrum (too deep), or poor healing responses on the part of the cornea. In most cases, successful treatment is possible and the affected cornea may be left with only mild scarring. Good vision is maintained in most eyes.

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Feline Eosinophilic Keratitis

Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO

BASIC INFORMATION

Description

Eosinophilic keratitis is the development of a pink, white, or gray film in the cornea of cats. This film often contains white blood cells called eosinophils (hence, the name). The condition may be accompanied by calcium deposition in the cornea and may also involve the third eyelid and the outer eyelids.

Eosinophilic keratitis may be diagnosed in one or both eyes. The disease arises in cats of all ages but is most common in cats 4 years or younger. Neutered (castrated) male cats are affected more often than females. The condition occurs in domestic shorthaired and longhaired cats more often than in purebred cats.

Causes

The exact cause of the disease is unknown. Feline herpesvirus (FHV) infection may be present in many affected cats (up to 76%), but whether this is a cause or only an opportunistic infection is unknown.

Clinical Signs

A pink, white, or gray film begins at the upper-outer edge of the cornea, or sometimes at the lower edge of the cornea, behind the third eyelid. This film slowly spreads across the cornea, and firm, gritty, white calcium plaques may develop on the surface. If the condition is left untreated, the cornea becomes thickened, irregular, and opaque. Corneal ulcerations may also occur.

The underside of the eyelids and the entire third eyelid may become red and thickened. Squinting and pain can occur from the eyelids blinking over the gritty, calcified areas or from corneal ulceration. Although tearing may be seen, usually a thick discharge is present on the surface of the eye. In severe cases, the cornea becomes infected and vision is decreased.

Diagnostic Tests

A tentative diagnosis can often be reached by finding the classic changes in the cornea. The diagnosis is confirmed by taking cell samples from the eye and finding eosinophils or mast cells (another type of white blood cell) in the samples. Samples may also be submitted for FHV testing. Other causes of corneal inflammation are eliminated by a thorough examination that may include tear testing, fluorescein staining, and glaucoma testing.

TREATMENT AND FOLLOW-UP

Treatment Options

Eosinophilic keratitis usually responds to topical steroid medications. In severe cases, injectable steroids may also be placed in the conjunctiva of the eye, or oral steroids may be given. Steroid therapy may be delayed if a corneal ulcer is present, because the steroids may make the ulcer worse. In these cases, the eye may be treated with topical antibiotics and/or antiviral medications until the ulcer has healed.

Additional treatment for FHV may be considered, including oral lysine and antiherpes drugs such as famciclovir. Topical cyclosporine has been used with success in a small number of cats. For cats that do not respond or do not tolerate these medications, oral megestrol acetate may be tried. This medication requires careful monitoring because of its potential serious side effects, including diabetes mellitus (sugar diabetes), weight gain, and behavioral changes.

Once the corneal film has receded, the medications are slowly tapered to the lowest dose that keeps the condition in remission. In some cases, long-term oral lysine may be recommended to try and suppress the FHV infection.

Follow-up Care

Recheck visits are needed to assess response to treatment and to check for complicating factors, such as corneal ulcers. Examinations are performed until the cornea is clear and then periodically thereafter to monitor for recurrences. Report any worsening of the signs or any onset of pain (squinting or increased tearing) immediately to your veterinarian. If the eye becomes painful while a topical steroid is being given, stop the drug until the eye can be re-examined.

Prognosis

This condition can be easy or difficult to control. The disease is more difficult to treat when active herpesvirus infection and corneal ulcers are also present. Medications must often be given consistently for several weeks to months to bring the condition under control.

The condition can often be controlled but may not be cured. Recurrences (as high at 64%) are possible as the medications are tapered and can also develop months to years later. If only one eye is affected originally, the second eye may be affected at a later date.

Mildly affected corneas often return to normal. In moderate to severe cases, some cloudy corneal scarring or crystalline fatty deposits may remain in the corneas. Good vision is usually maintained in most adequately treated eyes.

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Tags: Small Animal Practice Client Handouts

Sep 11, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

Fastest Veterinary Medicine Insight Engine

13: Diseases of the Eye

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