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Eye Problems in Dogs

Eye and eyelid diseases are traditionally divided into congenital-developmental and hereditary, trauma, inflammatory, immune-mediated and others, and eye and eyelid tumors. The difference in the orbital anatomy in the different breeds of dogs can predispose particular breeds to certain eye and eyelid diseases. For example, the deep and large orbits of giant and large breeds can predispose them to entropion and chronic conjunctivitis. The shallow orbit of the brachycephalics predispose these breeds to corneal exposure.

Eye diseases are often associated with:

  • Diabetes mellitus (cataract formation)
  • Hypocalcemia (cataracts)
  • Hhyperadrenocorticism (corneal disease, cataracts, and lipemia retinalis)
  • Hypothyroidism (keratoconjunctivitis sicca, intraocular hemorrhages from elevated systemic blood pressure, and lipemia retinalis [hyperlipidemia])

The following eye disorders often indicate that your pet has blood or blood vessel (vascular) diseases or disorders:

  • Intraocular hemorrhage - discharge of blood from the eyeball blood vessels
  • Retinal detachment - a condition of the eye in which the retina has separated from the choroid
  • Secondary glaucoma
  • Papilledema, or choked disk - swelling and protrusion of the blind spot of the eye caused by an abnormal excess accumulation of fluid in connective tissue (edema or dropsy)

Your dog's red eye may signal an eye problem requiring treatment from eye drops to emergency surgery. Red eye in dogs and cats may signal many inflammatory conditions and infectious diseases.

Conjunctivitis

Conjunctivitis is inflammation of the mucous membranes of the eye is the most common eye disease of all domestic animals," says Dr. Ralph Hamor, veterinary ophthalmologist at the University of Illinois Veterinary Medicine Teaching Hospital in Urbana. Dogs with allergies and purebred cats are prone to conjunctivitis. The eye reddens because of the increased flow of blood, and you may see swelling of the mucous membranes. Viruses or bacteria may cause conjunctivitis; parasites (such as ticks) and allergies are less common causes. Ticks can transmit several parasites that can cause conjunctivitis, keratitis and uveitis (3). Discharge may be clear or contain mucus, depending on severity of the infection.

"As a rule of thumb, conjunctivitis itches," explains Dr. Hamor. "Keeping the eye clean and eliminating the cause of the conjunctivitis with appropriate medication are keys to control." Keratitis- "Chronic superficial keratitis, also know as degenerative pannus, occurs primarily in German Shepherds but occasionally in other breeds," says Dr. Paul Gerding, also a veterinary ophthalmologist at the teaching hospital.

The disease causes pigmentation and superficial blood vessels on the eye. It's not that painful but can decrease vision if left untreated. Keratitis also occurs in chronic cases of keratoconjunctivitis sicca (KCS). KCS occurs when there is not enough moisture in the tear film. A thick, ropy mucous discharge is associated with this common ophthalmic disorder. In chronic cases, the corneal layer of the eye becomes infiltrated with blood vessels, pigmented, and harder because of the long-term irritation. Treatment involves tear stimulants and anti-inflammatories. "Eye ulcers are often associated with keratitis and may require surgical repair," adds Dr. Gerding.

In the case of external eye diseases such as conjunctivitis, keratoconjunctivitis sicca (KCS) and superficial corneal ulcers, eyedrops containing an antibacterial agent are often prescribed. Several daily instillations of eyedrops over several days are required for successful treatment. Eyedrops have several disadvantages, the biggest one being rapid elimination of the drug from the corneal surface. To overcome the disadvantage of repeated instillations, scientists have developed a soluble bioadhesive ophthalmic drug insert (BODI) that can be placed in the lower cul de sac of the eye. This BODI reduces the treatment to a single application and improves the efficiency of the treatment.

Herpes Viral Conjunctivitis. Conjunctivitis in cats is usually of viral origin and usually that means a Herpesvirus (Feline herpesvirus-1 to be specific). Herpes infection is extremely common in young kittens especially those facing other stresses (fleas, poor nutrition, environmental cold etc.). Feral kittens, outdoor kittens, shelter kittens, etc. are all high risk for Herpes infection.

Blood in the Anterior Chamber of the Eye. Bleeding in the eye generally results from trauma, inflammation, or other defects. Bleeding from trauma may need to be surgically corrected. Uveitis and tumors can bring about growth of new blood vessels, which are inherently leaky and may cause blood to accumulate. If the eye has progressed to glaucoma, removal of the eye may be necessary.



For further information about a suspected eye problem in your pet, contact your local veterinarian.

Inflammation of the Eyelids and Cherry Eye

Eyelids may become inflamed from dermatitis; a bacterial, parasitic, or fungal infection; a metabolic or immune system problem; tumors; trauma; or sun damage. Treatment varies by exact diagnosis. "Cherry eye" is a prolapse of the gland of the third eyelid. It commonly affects young dogs, especially beagles, cocker spaniels, Pekingese, and bulldogs. "The gland protrudes and becomes irritated and inflamed," explains Dr. Hamor. "If one eye has cherry eye, the other eye could be predisposed to it as well." Treatment for cherry eye is surgical replacement of the gland.

More About Cherry Eye in Dogs and Cats [...]

Blepharitis

Blepharitis in a dog
Photo courtesy of ucdavis.edu

An inflamed eyelid is usually the result of blepharitis. This is an infection of the eyelid's edges, which become sore, red and encrusted with scaly skin. Signs may include a thick discharge from the eye(s); spasm of eyelid muscle, especially when exposed to light; swelling and hardening of the eyelid; abcesses; scales and crust; inflammation of the inner surface of the eyelid (conjunctivitis) and loss of skin due to scratching or rubbing (excoriation).

Causes of blepharitis include:

  • Allergies to drugs, soaps, shampoos, and food.
  • Insect bites or flea bites.
  • Cat claw injury.
  • Chemical burns
  • Parasitic infections such as dermatophytosis, demodicosis (dogs and cats), and sarcoptic mange (dogs).
  • Chronic inflammatory conditions such as systemic lupus erythematosus (SLE)
  • Dermatitis caused by nutritional imbalances, including zinc deficiency (Siberian huskies, Alaskan malamutes, puppies) and fatty acid deficiency.
  • Endocrine system disorders (hypothyroidism and hyperadrenocorticism in dogs) can contribute to the development of chronic blepharitis.
  • Congenital eye abnormalities such as entropion (when the margins of the eyelids begin to turn inward), lagophthalmos (the inability to close, or poor closure, of the upper eyelid), trichiasis (when the eye lashes are misdirected toward the eye ball and scratch its surface) can contribute to the development of blepharitis.

If blepharitis is a result of other ongoing health conditions, those should be treated first. It is usually recommended to use warm compresses with an eye cleansing solutions such as Eye Scrub (CIBA), sold in individual packets in most pharmacies over the counter to remove crusts. Avoid getting the solution on the eye surface. The hair around the eye must be clipped short. Bacterial blepharitis is treated with antibiotics for at least 3 weeks. Because blepharitis can be a stubborn problem, be sure to follow your vet's instructions and use any prescribed medications as directed.

Scleritis

Scleritis is inflammation of the sclera, opaque white outer coat enclosing the eyeball. Scleritis may result from an underlying parasitic disease, such as toxoplasmosis (3) or lyme disease. "Scleritis usually involves only one eye. The red area may develop suddenly and be lumpy, immovable, and hard," says Dr. Gerding. It is often treated with steroids. Scleritis and uveitis, incidentally, can result in loss of the eye.

Uveitis

Uveitis is "Inflammation of part or all of the uveal tract is a very common eye problem in domestic animals and human beings," says Dr. Hamor. The uvea surrounds much of the eye with blood vessels. Your pet may show signs of eye pain such as an overflow of tears, eyelid spasms, sensitivity to light, recession of the eyeball into the orbit, and small pupils. If untreated uveitis harms vision. Uveitis may result from an underlying parasitic disease, such as toxoplasmosis.3

Glaucoma

"Glaucoma, if not treated immediately, can lead to irreversible blindness. A dog with glaucoma deserves the same emergency status as a dog that has been hit by a car," says Dr. Hamor. "Veterinarians may see glaucoma in 8 percent of all canine patients." Glaucoma is an elevation of pressure in the eyeball because an obstruction prevents fluids in the eye from flowing out. Signs of glaucoma include cloudy pupils, large pupils, and redness. "Treatment of acute glaucoma by the primary care veterinarian should be directed toward one goal—rapid reduction of pressure in the eye before permanent blindness occurs. Medical therapy must be started immediately after diagnosis in order to preserve vision," says Dr. Hamor. Recent studies show that glaucoma may result from yeast infection caused by yeast bacteria (Candida albicans). Breeds that consistently featured among the highest for glaucoma prevalence from the period 1994-2002 included American Cocker spaniels, Basset Hound, Wire Fox Terrier, Boston Terrier, Siberian Husky, Cairn Terrier, Chow Chow, Norwegian Elk Hound, and Miniature Poodle.

Cataracts

Cataracts are white opacities in the lenses of the eyes that impair vision or cause blindness. Several breeds of dogs are reported to suffer from inherited cataracts: Miniature Schnauzer, Boston Terrier, Golden Retriever, Labrador Retriever, Chesapeake Bay Retriever, Siberian Husky, American Cocker Spaniel, Old English sheepdog, Standard Poodle, Welsh Springer Spaniel and German Shepherd Dog. Diabetes mellitus is a common cause of cataracts in which case they develop and progress rapidly. Cataracts may be present at birth (congenital) or develop later and are caused by infections (such as canine herpesvirus, canine parvovirus-2 and canine adenovirus-1), injuries, poor nutrition, radiation therapy or toxins. The only treatment for cataracts is surgical removal, performed if the cataracts significantly impair vision.

Watery Eyes

Entropion is a condition when the eyelashes turn inward. It is a common cause of eye watering. Clean the eyes carefully with a wet cotton pad, using separate pad for each eye and making sure any debris buildup in the corner of the eye is removed.
Eyes that constantly water will produce permanent tear stains that can hardly be completely removed. Their appearance can be reduced by clipping the hair short. Some staining is caused by hair falling in the eyes and causing them to water. Make sure that the top knot is kept tidy to prevent this in such breeds as Poodle, Shih Tzu, Lhasa Apso and Bearded Collie. Watery eyes, squinting and thick discharge from one or both eyes is seen in dogs affected by Trichiasis. In this condition some lashes grow inward and rub on the suraface of the eye. Districhiasis occurs when two eyelashes grow from a single follicle. The extra lash often is the one that causes irritation. Pekingese, Poodle and Bedlington Terrier, Shar Peis and St. Bernards often have this condition. These deformities can eventually cause scarring of the cornea so that it loses its normal transparency and impairs the vision. The only effective treatment of the abnormal lashes is surgical removal.

Corneal Diseases

The cornea is the clear front part of the eye that provides the first step in the collection of light on its journey to be eventualyy focused onto the retina, and most corneal diseases will be manifested by alterations in corneal transparency.. The cornea is an exquisitely innervated tissue, and defects in corneal integrity are accompanied by pain, which is demonstrated by squinting.

Corneal dystrophy in a dog
Photo courtesy of
ucdavis.edu

Corneal dystrophy is a group of hereditary disorders of the cornea, which may be present at birth but more frequently develop slowly throughout life. In this condition, grayish-white, crystalline opacities develop in and around the central area of the cornea. These opacities are almost always present in the same area in both eyes. If the dystrophy affects the deepest corneal layer, as it does in the Boston Terrier, Chihuahua, and Dachshund, it can lead to corneal swelling and blindness.

Corneal ulcers may occur due to trauma or to irritation from entropion. In middle-aged or older dogs, ulcerations may occur spontaneously due to an inherent defect; these are called as Boxer ulcers, in recognition of the breed in the condition is seen most frequently. Infection may occur secondarily. Ulcers can be potentially blinding conditions; severity is dependent upon the size and depth of the ulcer and other complicating features.

Eye Infections

Infectious diseases often involve the eye tract and manifest themselves as iridocyclitis (inflammation of the iris and ciliary body, choroiditis (inflammation of the choroid of the eye - membrane that lies between the retina and the sclera of the eye), and panuveitis (inflammation of uvea - a layer of the eye made up of the iris, the ciliary body, and the choroid.) These infectious diseases may be caused by:

  • Viruses - (distemper, infectious hepatitis), rickettsial diseases:
    1. Canine monocytic ehrlichiosis (CME) - infection with or a disease caused by rickettsial bacteria of the genus Ehrlichia. Ocular symptoms: eye lesions, exudative retinal detachment (separation of the retina from the back of the eye with accumulation of fluid underneath the retina), anterior uveitis (inflammation of the uveal tract that affects the front of the eye), optic neuritis (inflammation of the optic nerve)
    2. Rocky Mountain spotted fever, an acute bacterial disease caused by a bacterium of the genus Rickettsia (R. rickettsii). Usually transmitted by ixodid ticks and especially by the American dog tick and Rocky Mountain wood tick. Ocular symptoms: conjunctivitis, anterior uveitis, retinal hemorrhages, cotton-wool spots (small areas of yellowish white coloration in the retina resulting of abnormal blood supply), and accumulation of fluid in the optic disc (edema).
  • Bacteria:
    1. Brucella canis - causes Brucellosis, a disease transmittable to humans; ocular symptom: uveitis; eye lesions
    2. Borrelia burgdorferi - causes Lyme borreliosis, the most common tick-borne disease in the United States; ocular symptoms: inflammation of various parts of the eye.
  • Fungi
    1. Blastomyces - cause Blastomycosis; ocular symptoms : swelling of the conjunctiva, purulent eye discharge.
    2. Coccidioides - cause Coccidioidomycosis; ocular symptoms: inflammation of the retina, choroid, iris and other parts of the eye.
    3. Histoplasma - cause Histoplasmosis, the second most common systemic fungal disease in cats; ocular symptoms: inflammation of the retina, and/or the choroid of the eye that may lead to vision loss.
    4. Cryptococcus - cause Cryptococcosis; ocular symptoms: inflammation of the retina and choroid of the eye (chorioretinitis).
    5. Aspergillus - cause Aspergillosis; ocular symptoms - uveitis, chorioretinitis, detachment of the retina.
  • Protozoa - animal-like, single-celled organisms many species of which live as parasites in animals and humans:
    1. Toxoplasma - causes toxoplasmosis, invades the tissues and may seriously damage the central nervous system);
    2. Neospora - causes neosporosis - a disease causing hind limb paralysis, ulcerative dermatitis, hepatitis, pneumonia, and encephalitis; ocular symptoms: blindness.
    3. Leishmania - causes Leishmaniasis, a diseases transmitted by the bite of sandfly; Cutaneous leishmaniasis (CL) presents as red pimples at lower or upper eyelid margins. If eyelid ulcers remain untreated, the parasite spreads from the skin of the eyelid and involves the conjunctiva, sclera, and iris, causing blindness.
    4. Hepatozoonosis - causes canine hepatozoonosis, a tick-borne disease of dogs; ocular symptoms: eye discharge containing both mucus and pus.
  • Parasites
    1. Thelazia (Eye Worms). Can be seen with naked eye, usually reside in the conjunctival sac and under eyelids, cause conjunctivitis, excessive tearing, sensitivity to light, keratitis, and, in the absence of treatment, cataracts and ulceration.
    2. Dirofilaria immitis causes a heartworm infestation affecting the heart and lung vessels of dogs, cats and occasionally humans. When the location is ocular, the worms are situated in the conjunctiva and can be extracted surgically.
    3. Toxocara canis is a nematode parasite residing inside the small intestine of young dogs. Toxocariasis regularly affects young children and is also known as hidden toxocariosis with no evident symptoms. When the location is ocular, the parasite lodges in the eyes. This is known as ocular larva migrans syndrome that often leads to loss of vision (typically on one eye), endophthalmitis (inflammation that affects the interior of the eyeball), abscesses, optic neuritis, keratitis or uveitis.
    4. Cuterbra sp flies - cause Cuterebriasis, in infestation caused by the larval stage of the flies. Ocular symptoms: blindness.
References
  1. Merck Veterinary Manual, Ophthalmology
  2. Inside of a Dog: What Dogs See, Smell, and Know. Alexandra Horowitz

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K-9 FACT BYTES

Blepharitis - inflammation of the eyelids characterized by redness, swelling, and dried crusts

Cataract - an eye disease that involves the clouding or opacification of the natural lens of the eye

Cherry Eye - prolapse of the nictitans gland of the third eyelid

Coloboma - congenital anomaly in which some of the structures of the eye are absent due to incomplete fusion of the fetal intraocular fissure during gestation

Conjunctivitis - inflammation of the conjunctiva of the eye, a transparent lubricating mucous membrane that covers the eyeball and the under surface of the eyelid

Ectropion - the turning outward (eversion) of the edge of the eyelid, resulting in the exposure of the conjunctiva

Entropion - the turning inward (inversion) of the edge of the eyelid, with the tarsal cartilage turned inward toward the eyeball

Epiphora - overflow of tears

Glaucoma - an eye disease that damages the optic nerve and impairs vision, sometimes progressing to blindness

Hemeralopia - inability to see clearly in bright light

Keratitis - inflammation of the cornea

Keratoconjunctivitis sicca - drying and inflammation of the conjunctiva as a result of insufficient tear secretion

Lens Luxation - a condition where the lens in the eye gets freed from its moorings and starts to move around inside the eye.

Nystagmus - involuntary movements of the eyeballs; its presence or absence is used to diagnose a variety of neurological and visual disorders

Optic Nerve Hypoplasia - underdevelopment of the optic nerve

Pannus - abnormal condition of the cornea, which becomes infiltrated with granular tissue and blood vessels

Progressive Retinal Atrophy - degeneration of the retina causing loss of sight

Retinal Dysplasia - congenital condition where retina is thrown into folds or rosettes

Retinoschisis - vitreoretinal dystrophy characterized by splitting of the neuroretinal layers; it occurs in two forms: degenerative retinoschisis and X chromosome-linked juvenile retinoschisis.

Scleritis - inflammation of the sclera, the whitish fibrous membrane that with the cornea forms the outer covering and protection of the eyeball

Uveitis - inflammation of the uvea of the eye, the part of the eye that contains the iris, ciliary body, and choroid

Persistent Pupillary Membrane - an inherited congenital condition where a spider web of tissue covers the pupils; these strands can cloud cornea, but vision is not impaired





Labrador Retrievers playing ball

Vision Streak

The canine eye lacks a fovea, but rather has a region termed the visual streak. The visual streak is an oval area of the retina located just above the optic nerve, and is positioned with its long axis on a horizontal plane, and is centered on the area of the retina closer to the nose. Like the fovea, it contains the highest concentration of photoreceptors and ganglion cells, and is the area that produces the greatest visual acuity. It is located in the tapetal area of the retina, which again aids in enhancing vision in dim light. The oval shape of the visual streak probably helps improve a dog's ability to scan the horizon, and the nasal location of the visual streak probably enhances a dog's ability to use peripheral vision.


Jaundice

Jaundice is yellowing of the whites of the eyes. There are many possible causes of jaundice:

  • Progressive disease causing increasing damage to the liver (hepatitis)
  • Urinary tract infection
  • Pancreatitis (inflammation of the pancreas)
  • Gallstones
  • Anemia (sickle cell )
  • Medications (recent anasthetic, acetaminophen, isoniazid, nitrofurantoin, methotrexate, sulfonamides, phenytoin, excessive intake of paracetamol, co-amoxiclav, flucloxacillin)
  • Viral infections toxoplasmosis

Underlying diseases must be treated quickly and monitored closely to avoid seious complications.

 




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