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Blepharitis is inflammation of the eyelids. Infection may be present. The eyelids contain many specialized structures that contribute to the overall health of the eyes (eg. protective eyelashes, special glands that secrete oil and mucus to help lubricate the eyes). All of these structures can develop diseases that produce discomfort and prevent proper lid function. Causes of blepharitis include birth defects, anatomical defects (eg. entropion, ectropion), neoplasia, infection, parasites, allergic reactions, autoimmune diseases, injuries and nutritional deficiencies. Signs may include excessive blinking (blepharospasms), rubbing the eyes, redness, tearing and swelling. Diagnosis is afforded by physical exam, cytology and/or biopsy, complete blood count, blood chemistries, immunological testing, culture and sensitivity. Treatment may include anti-inflammatories, antimicrobials, analgesics (pain killers), nutritional supplementation and/or surgery.
We place great value on eyesight and are deeply concerned and saddened when we discover a pet is blind. Loss of vision takes away a certain amount of independence. Pets, however, compensate very well and are free of the psychological trauma we associate with blindness. Their senses of smell, hearing and touch allow them to excellently perceive their surroundings. Cats and dogs do not drive automobiles, read novels or even care how their owners look. Pets are content to enjoy their owner’s presence and their other pleasures, sighted or otherwise, via the other senses. Even sighted, pets are provided for by their owners who wait on them, protect them, feed them and love them, and will continue doing so even if the pets are blind. Pets generally adapt well to blindness and are happy in a safe, familiar environment. Causes of blindness include degenerative diseases, anatomical defects, metabolic disorders, neoplasia, infections, inflammatory diseases, immune disorders, toxins and trauma. The cause may affect any part of the visual pathway from the front of the eye (eg. cornea) to the visual cortex of the brain. Signs of complete blindness can be obvious (eg. bumping into things) or subtle (hesitation to move in dim light). Diagnosis is afforded via complete eye exam and special tests (eg. tonometry (checks inner eye pressure), imaging tests, etc.). Treatment very rarely restores sight. Instead, most treatment is directed at making the pet comfortable and healthy.
Buphthalmos is a condition in which the eyeball is enlarged. It represents the final stage of prolonged and excessive elevated pressure (glaucoma) within the eyeball. Causes include degenerative disorders with the eye drainage system, neoplasia, inflammatory disorders, bleeding disorders and trauma. The enlarged eye may be painful and once the eye is noticeably enlarged, it is permanently blind. Signs of pain include listlessness, depression and rubbing the affected eye. Diagnosis is afforded via complete eye exam and associated tests for underlying disorders. Treatment is directed at underlying disorders and making the pet comfortable.
A cataract is any abnormal opacity (cloudiness) of the lens. The opacity may range from a tiny spot to total opacification. The lens is an disc shaped transparent structure that lies directly behind the iris and pupil. As light travels through the eye, it is refracted (bent) by the cornea, aqueous humor, lens and vitreous body to form an image upon the retina (back of eye). The cornea accounts for about 80% and the lens for about 20% of light refraction. Causes of cataracts include heredity, degenerative changes, metabolic defects and injuries. Cataract development ranges from a few days to years. Diagnosis is afforded via complete ophthalmic (eye) exam. Treatment is via surgical removal of the affected lens. Optionally, an artificial lens may then be inserted.
The eyelids contain numerous glands that open along the margins of the eyelids including the meibomian glands (tarsal glands). Their glandular secretion helps prevent tears from rapidly evaporating thereby helping to keep the eyeball lubricated and moist. Sometimes the Meibomian glands become clogged, distended and inflamed. This results in a small swelling on the eyelid called a chalazion. Treatment is surgical removal.
Collie Eye Anomaly
Collie eye anomaly (CEA) is an inherited and incurable disorder of Collies and to a lesser extent, Sheltland Sheepdogs. Its abnormalities may be detected at 5-8 weeks of age. The disease is usually asymmetric, affecting one eye more seriously than the other. The anomaly is characterized by small eyeballs, retinal defects and the disorder generally does not worsen as the dog ages unless there is retinal detachment. Retinal detachment is rare but may occur in serious cases and usually results in blindness of the eye. Selective breeding of normal animals will significantly reduce the incidence of Collie eye anomaly. It is an autosomal recessive trait, which means that both parents must be genetic carriers of the defect for the disorder to affect their pups. Clinically, signs of the disease are not very detectable. Most dogs with this disorder retain adequate functional vision. Diagnosis is afforded via complete ophthalmic exam. CEA has no treatment. Retinal detachment may be treated with limited success via laser surgery.
Conjunctiva is the pink tissue that lines the inner surface of the eyelids and covers the exposed portion of the eyeball, except for the clear, transparent cornea. It contains special glands whose secretions help maintain normal eye health. Conjunctivitis is an inflammation of the conjunctiva. It may affect one or both eyes, depending upon the cause. Causes of conjunctivitis include birth defects, eyelid defects, metabolic disorders, neoplasia, bacteria, viruses, fungi, foreign matter, chemicals, polluted water or smoke. Signs include redness, swelling and pain. Diagnosis is afforded via physical exam, complete ophthalmic exam, cytology, culture and sensitivity. Treatment may include anti-inflammatories, antimicrobials, eye washes, cool compresses as well as surgery (eg. with neoplasia and abnormalities) and the correction of underlying disorders.
Contusion of the Eye
Eye contusion (bruising of the eye) is an injury caused by a blow to the eye or its surrounding tissue. The injury may cause mild to severe bleeding within the eyeball yet have few or no external signs.
The cornea is the transparent front of the eyeball. It is less then 1 millimeter thick, consists of several layers, is very sensitive and readily reacts to irritants from both outside and inside the eye. The cornea’s transparency depends on a number of factors that maintain correct water content within the corneal tissue. Changes in any of these factors through injury or disease may cause the cornea to lose its transparency and become partially or totally cloudy. Corneal cloudiness may be caused by birth defects, metabolic disorders (eg. diabetes mellitus), infection, inflammation, allergic reactions, trauma, chemicals and other irritants. Diagnosis is via complete eye exam. Treatment may include correcting underlying disorders, anti-inflammatories, antimicrobials, immunologic therapy, contact lens and/or surgery (eg. conjunctival flaps, corneal repair, keratectomy).
Dermoids are islands of skin placed on the cornea, conjunctiva and/or eyelid during fetal development. Dermoids contain structures normally found in skin, such as hair, fat, oil glands and regular skin layers. Hair arising from the dermoid may cause mild to severe eye irritation and obstruct vision. Dermoids generally do not enlarge. They are inherited in Burmese cats and possibly German Shepherds, but do occur in other breeds of dogs. Signs include excessive blinking and tearing as well as red eyes. Diagnosis is via ocular (eye) exam. Treatment is via surgical removal.
A descemetocele is an eye emergency! The cornea is the clear front layer of the eyeball and is composed of 4 distinct layers. The descemetocele is the thin, clear bulge consisting of the inner layers of the cornea protruding through the damaged outer corneal layers. The delicate descemetocele may readily rupture and immediately threaten vision in that eye. Causes include any disease or injury that results in a deep corneal ulcer. Sign of a descemetocele is a distinctive bulge protruding from the injured cornea. Diagnosis is afforded via complete eye exam and fluorescein dye. Treatment may include antibiotics, antimicrobials, contact lens and surgery (eg. conjunctival flap, corneal repair, etc.)
Distichiasis is the condition in which eyelashes appear along the lid margin(s) emerging from the meibomian glands (oil glands) where ordinarily they should not grow. The eyelashes contact the cornea and cause irritation. This condition is common in Cocker Spaniels, Golden Retrievers and Shih Tzu breeds.
Trichiasis is the condition in which the eyelashes grow from normal areas but turn inward and touch the eyeball.
Both conditions may cause excessive tearing, discomfort and serious injury (eg. ulceration)to the eye. Diagnosis is via ocular exam. Treatment may include cryoepilation or electroepilation. In some cases, however, the conditions cause no harm or discomfort, and treatment is not required.
Ectropion is the turning out (eversion) of the eyelid. In addition to being unattractive, ectropion can cause irritation through exposure of the sensitive inner lining of the eyelids and eyeball to irritants. It may allow drying of the eyeball due to increased tear evaporation and/or inefficient spreading of the tears during the blink reflex. Treatment is via surgery.
Enucleation is the surgical removal of the eyeball and/or its contents. It is a last resort treatment for very serious eye trauma or diseases, after all other alternatives have been carefully considered. Experienced surgeons and modern surgical techniques allow minimum disfigurement and maximum comfort to the patient. Either the eyeball is completely removed and the eyelids are sutured permanently closed. Alternatively, the eyeball contents are removed (evisceration) and a prosthetic globe is implanted. Either procedure is an acceptable, humane alternative to destruction of the animal. Animals adjust very well to single-eyed vision.
The sclera is the outer covering of the eyeball (white of the eye). The thin outer layer of the sclera is called the episclera. Episcleritis is an inflammation of the episclera. The cause is believed to be due to a complex allergic (immune) reaction. It appears as a small, immovable lump or swelling around the corneal margin. With significant reaction, small blood vessels may grow into the cornea and cause it to become cloudy. Diagnosis is afforded via physical exam, complete ocular exam, biopsy and response to therapy. Treatment may include corticosteroids and/or immune suppressive medication.
Exophthalmos an excessive protrusion of the eyeball. It is considered normal in the small, flat-nosed breeds with prominent eyes (brachycephalic breeds). As long as the eyes are not damaged, no correction is required. Occasionally the eyes protrude so much that the eyelids cannot close completely and serious corneal damage results from exposure and dryness. In these rare cases surgical correction is indicated. A type of exophthalmos called transient exophthalmos may occur in young German Shepherds. It corrects itself as the pup matures and treatment is rarely required. Causes of abnormal exophthalmos include abscesses, tumors and salivary cysts. Diagnosis is afforded via radiographs (x-rays), laboratory tests, aspiration cytology (fluid withdrawn through a needle) and biopsy. Treatment is directed at the underlying cause and may include antibiotics, drainage, flushing and surgery.
Glaucoma is a disease in which pressure within the eyeball is abnormally elevated to dangerous levels. It is one of the most common causes of blindness in dogs and cats. Normal pressure within the eye is maintained by a delicate balance between production and escape of internal eye fluid (aqueous humor). If fluid drainage is blocked, the internal eye pressure may rise to dangerous levels (glaucoma) that can permanently destroy the retina and injure other vital internal structures of the eye. If glaucoma persists over a long enough time, the eyeball may become enlarged. Breeds predisposed to acute glaucoma are the American and English Cocker Spaniels, English Springer Spaniel, Miniature Poodle, Beagle, Basset Hound, Siberian Husky, Norwegian Elkhound, Samoyed, Malamute, Chow Chow, Shar Pei and Afghan. The causes of glaucoma include blockage of the drainage passage due to birth defects (possibly inherited), metabolic disorders (eg. hyperlipidemia), neoplasia, inflammatory conditions, trauma, toxins, blockage of the pupil and lens disorders. Signs include enlarged eyeball, prominent, engorged blood vessels upon the eyeball surface, redness, pain, rubbing the eye, blindness, tearing, blinking, dilated pupil and corneal cloudiness. Diagnosis is afforded via physical exam, complete ocular exam, tonometry (pressure check), complete blood count and blood chemistries. Treatment is directed at any underlying disorders as well as reducing intraocular pressure (IOP). Treatment may include medication that reduces fluid production, opens drainage channels, increases drainage through existing channels and/or surgery (eg. place drains, cryosurgery, etc.).
Hyphema is the presence of blood within the front compartment (anterior chamber) of the inner eye, and is a sign of a serious problem. Extensive bleeding within the eye can lead to serious consequences, including blindness. Causes include bleeding disorders, inflammation, infection, hypertension, toxins and trauma. Signs include redness, glaucoma and impaired vision. Diagnosis is via complete ocular exam. Treatment is directed at the underlying disorder.
Keratitis is inflammation of the clear front layer of the eyeball (cornea). The cornea has 4 distinct layers, is less then a millimeter thick, transparent and normally is devoid of blood vessels and pigment. Causes of keratitis include degenerative disorders, birth defects, metabolic disorders, neoplasia, irritation, immune or allergic reactions, infection, trauma and toxins. Signs include pain, cloudiness, pigmentation, vessel ingrowth and ulcerations. Keratitis is described according to the corneal layers affected and the shape or nature of the abnormality. These include superficial, interstitial, deep, ulcerative, pigmentary, punctate, dystrophic, allergic and degenerative keratitis. Diagnosis is afforded via physical exam, complete ocular exam, complete blood count, blood chemistries, cytology and laboratory tests. Treatment is directed at any underlying disorders and may also include anti-inflammatories and antimicrobials.
Keratoconjunctivitis Sicca (KCS or dry eye)
Dry eye is a disease of insufficient tear production whereby the cornea dries out. Tears are produced from the tear (lacrimal)glands positioned above each eyeball and the accessory glands distributed throughout the front of the eyes, including the eyelids. Disease or destruction of these tear glands may reduce tear production to produce KCS (keratoconjunctivitis sicca). Causes include nerve degeneration, metabolic disorders (eg. hypothyroidism), neurologic disorders (eg. facial nerve paralysis), neoplasia, immune reactions, infections, trauma, chemicals and drugs (eg. sulfadiazine). Signs include discharge, conjunctivitis, excessive blinking, dry/dull appearance to the eye and even blindness. Diagnosis is afforded via physical exam, ocular exam, Schirmer tear test, various laboratory tests. Treatment may include cyclosporine, artificial tears, tear stimulants (eg. pilocarpine), mucolytics, antibiotics, corticosteroids and if all else fails, transposition of the parotid salivary gland duct.
The lens bends light rays to produce a sharply focused image upon the back of the eye (retina). Lenticular sclerosis (hardening of the lens) results from normal aging. New lens fibers are continually being formed by cells in the outer portion of the lens. As new fibers are laid down, older fibers are pushed toward the lens center. Over the years more and more fibers become compressed within the lens center and the crystal-clear lens is obscured by the compressed fibers. The lens becomes bluish and the once clear pupil appears cloudy. It does not cause blindness but can diminish normal vision. Animals usually retain sufficient vision to function well within a familiar environment. No treatment is required unless a true cataract forms in addition to the lenticular sclerosis.
Microphthalmos is a condition in which the eye is smaller than normal. It is inherited in the Austrlian Shepherd, Collie, Shetland Sheepdog, Old English Sheepdog, Akita, American Cocker Spaniel, Miniature Schnauzer, Doberman Pinscher, Samoyed, Cavalier King Charles Spaniel and Lancashire Heeler. Microphthalmos also occurs in cats. It also may be concurrent with other inherited retinal defects, such as Collie eye syndrome. It generally results from abnormal development of the fetal eye. Teratogens (causes of birth defects) such as viruses, drugs, live virus vaccines may be responsible. Signs include a small cornea which may be misshapen. Diagnosis is afforded via ocular exam and corneal measurement. There is no treatment. The condition is painless. If internal eye structures are abnormal, vision may be abnormal, otherwise vision is intact.
Nasolacrimal Drainage Disorders
The nasolacrimal drainage apparatus is the escape route for tears and consists of puncta (2 on the inner part of each eye), lacrimal sacs (one at inner part of each eye, each draining 2 puncta) and the nasolacrimal ducts (tear ducts) which extend from each lacrimal sac along the muzzle under the lining of the roof of the nose. Disorders of the nasolacrimal drainage apparatus include congenital deformities (birth defects), infections, foreign bodies such as plant awns or seeds, trauma and tumors affecting one or both sides. Signs include overflow of tears, redness or swelling in the inner corners of the eye. Diagnosis is afforded via ocular (eye) exam, fluorescein dye studies and fine probe placement. Treatment may include hydropulsion, antimicrobials, anti-inflammatories and surgery.
The nictitans flap is a surgical procedure that uses the third eyelid (nictitans membrane) as a temporary, living bandage to cover the eyeball. It promotes healing and protects the cornea thereby reducing pain.
Nictitans Gland Protrusion (cherry eye)
The third eyelid (nictitans membrane) lies between the eyelids and the eyeball at the inside corner of each eye. Its purpose is to protect the eye and spread tears over the cornea. The third eyelid also contains tear producing glands which contribute to the overall lubrication of the eye. The gland of the third eyelid lies within the third eyelid and if inflamed may protrude over the free edge of the third eyelid. As a result, the exposed, sensitive tissue becomes very irritated and painful. The reddened, swollen tissue resembles a cherry; hence, the layman name “cherry eye”. Treatment may include medical management (eg. anti-inflammatories and antimicrobials), surgical replacement into the third eyelid or surgical excision of the gland.
The eyelids of newborn puppies and kittens do not open until 7 to 14 days of age. Ophthalmia neonatorum is a serious infection located directly behind the closed eyelids. The cause is bacteria that have entered the eyes before, during or after birth. Signs include reddened, swollen and painful eyelids. The eye may be damaged and vision lost. Diagnosis is afforded via physical exam, cytology, culture and sensitivity. Treatment includes antibiotics and irrigation.
Pannus is a progressive, degenerative disease of the cornea (transparent front of the eyeball). It primarily affects German Shepherds, but may affect other breeds. Causes may include immune reactions whereby the body attacks its own corneal cells and ultraviolet light trauma (excessive sun exposure). Signs include visible blood vessels, pigment and scar tissue within the cornea. If the disease continues, the cornea can lose its transparency, and blindness may result. Diagnosis is afforded via complete blood count, laboratory tests (eg. immune tests), cytology and complete ocular exam. Treatment may include corticosteroids, immune suppressive drugs and surgery.
Persistent Pupillary Membranes
Persistent pupillary membranes (PPM) are strands or remnants of an embryonic membrane that extends from the iris to the inner surface of the cornea. Small, white areas may appear on the cornea or lens where the PPM attaches. These cause little problem to your pet unless so many exist that they impair vision. Most opacities greatly diminish with maturity. PPM is inherited in Basenjis and probably in other breeds.
If the eye becomes severely injured or diseased, various parts may be replaced by scar tissue and are rendered unfunctional. Degenerative changes may take place over several days to weeks. As the degeneration progresses, colors begin to fade, the eye becomes smaller, irregular in shape and possibly blind. This final state is a “phthisis bulbi”. If no infection is present, there is usually no pain or danger to the overall health of your pet.
Posterior Segment Disorders: Acquired
Acquired posterior segment eye disorders are abnormalities of the back part of the eyeball that occur after birth. Inherited forms of acquired posterior segment eye disorders include progressive retinal atrophy (PRA), central progressive retinal atrophy and hemeralopia. Non-inherited forms include inflammatory, nutritional, vascular, traumatic or neoplastic (tumor). Blindness (partial, complete, temporary, or permanent) may result from acquired posterior segment eye disorders.
Posterior Segment Disorders: Congenital
Congenital posterior segment eye disorders are abnormalities of the back of the eyeball that are present at birth. They may be inherited or may be caused by non-inherited diseases, toxins, poor nutrition, radiation, drugs or infection. Examples of congenital posterior segment eye disorders include Collie eye anomaly, multiple ocular anomalies, vitreoretinal dysplasia, retinal dysplasia, optic disc colobomas and optic nerve hypoplasia.
Progressive Retinal Atrophy
Progressive retinal atrophy (PRA) is a broad group of genetic retinal diseases in which the final outcome is degeneration and loss of retinal structure. The retina lines the back of the inner eye and contains the light-sensitive rods and cones that change light into signals to the brain. The retina is similar to the film in a camera. There is no pain or discomfort associated with PRA but it leads to permanent blindness. Due to PRA’s slow progress, most pets adapt very well to the gradual loss of sight and owners may not even realize their pet is becoming blind.
Retinal dysplasia is an abnormal congenital (present at birth) development of the retina. Causes include intrauterine viruses, nutritional deficiencies, injury during fetal development, irradiation and genetic influences. Any breed can be affected, but only a few transmit the disorder genetically. These include Bedlington Terriers, Springer and Brittany Spaniels, American and English Cocker Spaniels, Shetland Sheepdogs, Rottweilers, Australian Shepherds, Borzois, color-dilute Collies, Labrador Retrievers and Harlequin Great Danes. The disorder may or may not cause blindness. Diagnosis is via ocular exam. Treatment is by prevention (eg. vaccinations, proper breeding, avoidance of infection, etc.)
Retrobulbar abscess is an accumulation of pus behind the eyeball. The cause is bacteria that have entered through a wound or have been transported by the blood from elsewhere in the body. Signs include protrusion of the eyeball, pain when the mouth is opened and anorexia. Diagnosis is afforded via laboratory tests, radiographs (x-rays) and analysis of fluid samples. Treatment includes antibiotics, drainage and pain medication.
Ulcerative keratitis is inflammation and ulceration of the cornea. Causes include degenerative disorders, inborn weaknesses, metabolic disorders (eg. diabetes mellitus, hyperadrenocorticism, hypothyroidism), neoplasia, nutritional deficiencies, infections, trauma and chemicals. Signs include excessive blinking, sensitivity to light, tearing, pain, redness, vascularization of the cornea and corneal cloudiness. Diagnosis is afforded via ocular exam, cytology, fluoroscein stain (stains ulcer), laboratory tests, complete blood counts and urinalysis. Treatment may include antimicrobials, surgical therapy (eg. conjunctival flaps, keratotomy, etc.) and contact lens.
Uveitis is inflammation of the iris, ciliary body and choroid (major structures of the eye).
Uveitis is described as:
- Anterior uveits: affecting the iris and ciliary body.
- Posterior uveitis: affecting the choroid.
- Uveitis: affecting the iris, ciliary body and choroid.
Causes include metabolic disorders, neoplasia, inflammation, infection (viruses, bacteria, fungi), immune-medicated reactions (a complex allergic-type reaction), trauma and toxins. Signs include discharge, excessive blinking, small pupil, corneal cloudiness, redness, sensitivity to light and even blindness. Diagnosis is afforded via physical exam, complete blood count, blood chemistries, cytology, biopsy, ocular exam, tonometry (checks eye pressure), fluorescein stain (checks for corneal ulceration), serology and radiography (x-rays). Treatment may include atropine, anti-inflammatories, antimicrobials, corticosteroids, pain medication and/or immunosuppressive drugs.