Inherited eye disorders

Cataracts

roblib — Tue, 13 Apr 2010 17:25:01 +0000

What is ... ?:

A cataract is any opacity or loss of transparency of the lens of the eye. The opacity may be confined to a small area of the lens or capsule, or it may affect the whole structure. A complete cataract affecting both eyes will result in blindness, whereas small non-progressive cataracts will not interfere with vision. Primary cataracts occur in some breeds; in other breeds the cataract may develop secondarily to another inherited disorder such as progressive retinal atrophy or glaucoma.

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How is ... inherited?:

The genetics have not yet been defined for most affected breeds. In others, the mode of inheritance is autosomal recessive, autosomal dominant, or with incomplete dominance.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

This depends on whether the cataracts are localized to a small area or are more general, and whether they affect one or both eyes. A small cataract in one eye will not affect your dog's vision at all. At the other end of the spectrum, cataracts may progress rapidly or slowly to cause complete blindness.

Congenital cataracts or those that develop at a young age may mature and be reabsorbed, resulting in improved vision. This is unpredictable. In the process of resorption, liquefied lens material may leak into the eye causing inflammation and possibly glaucoma.
With their acute senses of smell and hearing, dogs can compensate very well for visual difficulties, particularly in familiar surroundings. In fact owners may be unaware of the extent of vision loss. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as constant as possible, introducing any necessary changes gradually, and being patient with your dog.

How is ... diagnosed?:

You may suspect your dog is having visual difficulties and/or you may notice discoloration of your dog's pupil(s). Your veterinarian will be able to see the cataract with an ophthalmoscope. Even when not causing visual problems, cataracts may be discovered on a routine ophthalmoscopic exam.

How is ... treated?:

Cataracts can be removed surgically. The decision whether to do so is based on several factors, such as whether the cataracts are progressive, the degree of visual impairment, and the dog's temperament. To prevent postoperative problems, the dog must be cooperative and quiet, especially in the first week following surgery.

Breeding advice:

It is prudent to assume cataracts are inherited unless another specific cause can be identified. Since some cataracts cause no clinical signs, it is worthwhile to screen dogs of affected breeds annually that are used in breeding programmes. Where cataracts are identified, affected animals, their parents and littermates should not be used for breeding.

The fact that the age of onset is fairly specific for different breeds is helpful in making decisions about breeding programmes.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

American College of Veterinary Ophthalmologists. 1996. Ocular Disorders Presumed to be Inherited in Purebred Dogs. Purdue University, W. Lafayette, Indiana.

Collie eye anomaly (CEA)

roblib — Tue, 13 Apr 2010 17:36:49 +0000

What is ... ?:

CEA is a disorder of the deep structures of the eye that affects collie breeds around the world. The four main changes are:

inadequate development of the choroid, a thin layer of blood vessels that delivers oxygen and nutrients to the retina (called hypoplasia of the choroid or chorioretinal dysplasia);
coloboma - a cleft or defect of the optic disc or adjacent areas;
staphyloma - an area of thinning in the sclera which is adjacent to the choroid; and
retinal detachment with or without haemorrhage - a complication associated with the other defects.

In its mildest form, there are minor changes in the choroid which will have little effect on sight. About 25 per cent of dogs with CEA have colobomas/staphylomas as well as choroidal hypoplasia. Retinal detachments occur in approximately seven per cent of dogs with CEA. Total retinal detachment will cause blindness.

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How is ... inherited?:

Inheritance is autosomal recessive with variable expression and pleomorphism (meaning that there is a wide range in clinical expression of the defect).

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Many dogs will have apparently normal vision unless retinal detachment with or without haemorrhage occurs, causing blindness in the affected eye. Retinal detachments are often one-sided and generally occur before 2 years of age.

How is ... diagnosed?:

Your veterinarian will be able to see the abnormalities in the back of the eye with an ophthalmoscope.

How is ... treated?:

There is no treatment.

For the veterinarian:

Choroidal hypoplasia - appears as an area lateral (temporal) to the optic disc with reduction or absence of pigment so that the underlying choroidal vasculature is seen; the choroidal vessels may be reduced in number and of abnormal shape; may see underlying white sclera. Once the retina changes to its adult colour (about 3 months of ages), the normal pigment in the retina may mask the changes in the choroid (so-called "go normal")
Coloboma - appears as an excavation of the optic disc surface and sometimes adjacent ocular fundus
Retinal complications - detachment with or without haemorrhage

Breeding advice:

Minor lesions may not be detectable by ophthalmoscope after 3 months of age, so collies intended for breeding programmes should be examined early at 5-6 weeks of age. Even dogs with minor lesions (mild choroidal hypoplasia) should not be bred because their offspring may be affected with more serious forms of the disorder.

Because of the potential for serious eye disease with this trait, neither affected dogs, their parents, or their offspring should be used for breeding. Siblings of affected dogs should not be used either, unless eye exams before 3 months of age demonstrate that they are unaffected.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Gelatt, K.N. 1991. Veterinary Ophthalmology. p. 473-477. Lea and Febiger.

Corneal dystrophy

roblib — Tue, 13 Apr 2010 17:42:20 +0000

What is ... ?:

Corneal dystrophy is an inherited abnormality that affects one or more layers of the cornea. Both eyes are usually affected, although not necessarily symmetrically. Chronic or recurring shallow ulcers may result, depending on the corneal layers affected:

Epithelial dystrophy causes shallow painful erosions/ulcerations in the cornea.
With epithelial/stromal dystrophy, there are whitish crystalline lipid deposits, typically cholesterol, in the superficial layers of the cornea. This is thought to result from a disorder of normal lipid metabolism in the cornea. These deposits usually do not cause problems. You may notice a white to grey opacity in 1 or both of your dog's eyes.
Endothelial dystrophy affects the function of the endothelial cells. The result is a build-up of fluid in the cornea (corneal edema) which clouds the normally transparent cornea and may decrease vision. Edema may cause the eye to appear blue. Recurring non-healing shallow corneal ulcers occur as well.

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How is ... inherited?:

In the Siberian husky, corneal dystrophy has been shown to be an autosomal recessive trait, with variable expressivity. In Airedales, inheritance is sex-linked . The mode of Inheritance in other breeds has not been identified.

What does ... mean to your dog & you?:

corneal dystrophy - epithelial erosion: The dystrophy that occurs in Shetland sheepdogs occurs as many small gray-white opacities, which may be associated with painful shallow erosions of the cornea. In older boxers, dystrophy of the epithelium causes chronic corneal ulceration. These ulcers are painful and hard to clear up, and they often recur.

epithelial/stromal dystrophy: The opacity in your dog's eyes may become quite obvious over time. In most cases, the accumulation of lipid deposits does not affect vision. In some breeds such as Airedales (by 3 to 4 years of age) and beagles, the opacities may progress to the point where they impair vision.
endothelial dystrophy: Over time, the fluid build-up causes inflammation of the cornea and reduced vision. "Water blisters" (bullous keratopathy) may develop which can rupture and cause painful erosions or ulcers.

How is ... diagnosed?:

You or your veterinarian may notice one or several small white to gray areas in one or both of your dog's eyes. Magnification may reveal crystalline deposits within the deeper layers of the cornea or simply a haze.

If there are epithelial erosions, your dog may show signs of discomfort such as increased tearing, squinting and rubbing the eye. Your veterinarian will examine the eye for erosions or, in the case of edema, for bullous keratopathy. A fluoroscein dye test is used to check for corneal ulcers.

How is ... treated?:

For dogs that experience painful, shallow epithelial erosions (primarily boxers and Shetland sheepdogs), treatment is aimed at eliminating the lesions. This will involve medication in the eye. Surgical treatment may be required if chronic discomfort persists.

Most stromal dystrophies cause no discomfort and do not interfere with vision. No treatment is necessary.
In endothelial dystrophy, no treatment is necessary in the early stages of the disease. As the edema (or fluid build-up) in the cornea increases, dogs may develop "water blisters" (bullous keratopathy) which can rupture and cause painful erosions. Your veterinarian will prescribe eye medication appropriate for bullous keratopathy (hyperosmotic solutions) as well as treatment for ulcers if present. There are surgical treatments which can be performed by a veterinary ophthalmologist if the erosions persist or recur frequently despite medical therapy.

For the veterinarian:

In the Shetland sheepdog, Schirmer's tear test values are often reduced.

Breeding advice:

epithelial/stromal dystrophy: Even though opacities associated with these superficial corneal dystrophies are rarely dense enough to affect vision, affected dogs should not be used for breeding.

epithelial erosions and endothelial dystrophy: Affected dogs and their close relatives should not be used for breeding.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Murphy, C.J. 1992. Disorders of the cornea and sclera. In R.. Kirk and J.D. Bonagura (eds.) Current Veterinary Therapy XI Small Animal Practice, p. 1101-1111. WB Saunders Co., Toronto. good information on therapy

Dermoids

roblib — Tue, 13 Apr 2010 17:49:49 +0000

What is ... ?:

A dermoid is an area or fold of normal skin that forms in an abnormal area, usually on the cornea or conjunctiva. Dermoids affect one or both eyes and usually cause irritation.

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How is ... inherited?:

The mode of inheritance is not defined.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Very small dermoids may cause no problems. Larger ones are usually irritating to the surface of the eye and can interfere with vision.

How is ... diagnosed?:

Dermoids are diagnosed by their appearance.

How is ... treated?:

The abnormal patch of skin is removed surgically.

Breeding advice:

The inheritance of this condition is not clear; however it is best not to breed affected dogs.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Ectropion

roblib — Tue, 13 Apr 2010 18:03:20 +0000

What is ... ?:

Ectropion is a defect of conformation in which there is a sagging or rolling-out (eversion) of the eyelids. This results in abnormal exposure of the eye, which often leads to irritation.

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How is ... inherited?:

It is likely that ectropion is influenced by several genes (polygenic inheritance) that affect the skin and other structures that make up the eyelids, and that affect the way the skin covers the face and head.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Because of increased exposure of the eye, dogs with ectropion are prone to develop allergic or bacterial conjunctivitis - inflammation of the thin membrane which covers the periphery of the surface of the eye and lines the eyelids. Affected dogs may develop keratoconjunctivitis sicca because of reduced efficiency at wetting and cleaning the cornea.

Dogs who have had surgical correction for a defect such as ectropion are prohibited from exhibition in the show ring.

How is ... diagnosed?:

In addition to the sagging of the eyelids, dogs with ectropion commonly have a mucopurulent discharge in the eye, reddening of the exposed conjunctiva, and decreased tear production. To check the latter, your veterinarian will do a Schirmer tear test.

How is ... treated?:

With mild entropion, no treatment may be necessary. If secondary problems such as conjunctivitis develop, these are treated as required.

More severe ectropion can lead to chronic problems associated with eye irritation. In these cases, surgery is performed to remove a small wedge of tissue from the margin of the eyelid.

Breeding advice:

Ectropion is one of the eye conditions that is a result of selection by breeders and a demand by the public for such features as excessively prominent eyes and heavy facial folds. A responsible breeding programme will choose animals for breeding with a more normal head conformation, so as to select away from these exaggerated facial features and the problems associated with them.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Entropion

roblib — Tue, 13 Apr 2010 18:08:32 +0000

What is ... ?:

Entropion is the inward rolling of the eyelid, most commonly the lower lid. This irritates the surface of the eye (the cornea) and may ultimately cause visual impairment.

Entropion is a common hereditary disorder in dogs. Selection for a particular conformation, of exaggerated facial features with prominent eyes and/or heavy facial folds, has created or worsened this problem in many breeds.

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How is ... inherited?:

It is likely that ectropion is influenced by several genes (polygenic inheritance) that affect the skin and other structures that make up the eyelids, the way the skin covers the face and head, and the conformation of the skull.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The problem is usually evident before a year of age. Discomfort from entropion will cause increased tearing and squinting. Your dog may be sensitive to light and may rub at its eyes. Chronic irritation by the turned-in eyelid may cause corneal ulceration and scarring which is painful and, if not corrected, can impair vision.

Dogs who have had surgical correction for a defect such as entropion may not be exhibited in the show ring.

How is ... diagnosed?:

The inrolling of the eyelid is readily apparent. Generally both eyes are affected. Depending on the degree of corneal irritation and the duration, there will be other signs such as those mentioned above. Your veterinarian will evaluate the degree of entropion and use flourescein dye to determine if there is any corneal ulceration.

How is ... treated?:

Entropion is corrected surgically. If possible it is best to delay surgery until the dog is an adult since the involved facial structures are still growing and changing.

More than 1 operation may be required. It is better to correct the entropion conservatively and repeat the operation later if necessary, than to overcorrect causing ectropion. In breeds such as the chow chow that have particularly severe entropion related to heavy facial folds, several surgeries may be required.

For the veterinarian:

The use of topical ophthalmic anaesthetic to anaesthetize the cornea and conjunctiva will enable eliminatation of the spastic component of the entropion in order to better evaluate the anatomic component. This is important before surgery is performed.

Breeding advice:

Entropion is one of the eye conditions that is a result of selection by breeders and a demand by the public for such features as excessively prominent eyes and heavy facial folds. A responsible breeding programme will choose animals for breeding with a more normal head conformation, so as to select away from these exaggerated facial features and the problems associated with them.

The Vizsla Club of America has recognized entropion as an unacceptable problem in their breed, and advises breeders not to breed affected animals. Such leadership by breed clubs is important in discouraging this and other undesirable traits.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Slatter, D. 1993. Textbook of Small Animal Surgery. p. 856-889. W.B. Saunders Co. ,Toronto.

Exposure keratopathy syndrome (exophthalmos, lagophthalmos, and/or macroblepharon)

roblib — Tue, 13 Apr 2010 18:30:48 +0000

What is ... ?:

With this syndrome, there is chronic irritation of the surface of the eye (the cornea) because of increased evaporation of tears and increased corneal exposure. This is a result of a combination of anatomic features including exophthalmos (protrusion of the eyeball), lagophthalmos (inability to close the eyelids completely) andmacroblepharon (an exceptionally large eyelid opening, often associated with lower lidentropion). The result is inadequate blinking, and therefore reduced protection for the eye. Affected dogs experience chronic discomfort and are prone to ulceration of the cornea.

It is important to note that these anatomic features are normal for certain breeds, as a result of selection by breeders and demand by the public for a particular facial conformation with very prominent eyes, heavy facial folds and/or droopy eyelids. For example, the breed standard for pugs calls for a round head "with very large, bold and prominent eyes."
To avoid problems such as exposure keratopathy syndrome, breeders and dog owners are encouraged to choose dogs with less exaggerated facial features.

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How is ... inherited?:

The syndrome is associated with a combination of anatomic features that are influenced by several genes affecting skull and facial conformation.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Signs of chronic corneal irritation include reddening of the eye, increased tears, and discomfort (pawing or rubbing the eye). Affected dogs are prone to eye injuries from environmental insults (dust, twigs, et cetera). Corneal ulcers may develop due to increased corneal exposure.

Over time, pigmentation of the cornea may occur in response to chronic irritation. This may eventually interfere with your dog's vision.

How is ... diagnosed?:

The eyeballs are prominent and the eyes may be reddened from chronic irritation. If corneal ulceration has developed, the eye will be painful and your dog may paw or rub it. With lagophthalmos, you may notice that your dog's eyes do not close completely when s/he is asleep.

Your veterinarian may do a fluoroscein dye test to check for corneal ulceration.

How is ... treated?:

Tear substitutes provide only temporary relief. Surgical correction to reduce the size of the eyelid opening (permanent partial tarsorrhaphy) is usually effective in protecting the cornea over the long term. Where other associated eyelid defects such as entropion are present, several surgeries may be required.

Corneal ulceration, if present, must also be treated.

Breeding advice:

Exposure keratopathy syndrome is one of the eye conditions that is a result of selection by breeders and a demand by the public for such features as excessively prominent eyes and heavy facial folds. A responsible breeding programme will choose animals for breeding with a more normal head conformation, so as to select away from these exaggerated facial features and the problems associated with them.

Any dog that has required surgical correction to treat this condition should not be used for breeding, and may not be exhibited in the show ring.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Slatter, D. 1993. Textbook of Small Animal Surgery. p. 856-889. W.B. Saunders Co. ,Toronto.

Glaucoma

roblib — Tue, 13 Apr 2010 19:04:06 +0000

What is ... ?:

Glaucoma is a leading cause of blindness in dogs. It is the result of increased fluid pressure within the eye (elevated intraocular pressure or IOP). If the pressure can not be reduced, there will be permanent damage to the retina and optic nerve resulting in visual impairment. Complete blindness can occur within 24 hours if the IOP is extremely elevated or can occur slowly over weeks or months if the the elevation is mild. Glaucoma is usually very painful.

Glaucoma may be primary (inherited) or secondary to a number of eye disorders including luxation of the lens, tumours of the eye, and uveitis (inflammation of the eye).
Primary/inherited glaucoma causes an elevation of pressure within the eye because of abnormal drainage of fluid through the iridocorneal angle. When the angle at which the iris and cornea join is wide, the glaucoma is classified as open angle. If the base of the iris is pushed forward, the glaucoma is described as narrow angle.
Goniodysgenesis is characterized by an abnormal sheet of tissue in the angle where drainage normally occurs. This may or may not cause an elevation in IOP and glaucoma.
In pigmentary glaucoma, the obstruction to fluid drainage is caused by an abundance of pigmented cells within the iridocorneal angle and sclera. The increase in IOP is progressive and often results in blindness.

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How is ... inherited?:

Inherited open angle glaucoma is an autosomal recessive trait in beagles. Narrow angle glaucoma is inherited as an autosomal dominant trait in the Welsh springer spaniel. The mode of inheritance for glaucoma in other breeds has not been identified.

What does ... mean to your dog & you?:

Primary open angle glaucoma develops slowly over weeks to months. With closed angle glaucoma, which is much more common, there is usually a sudden, rapid elevation in the pressure within the eye. This affects all the structures in the eye. The effects on the optic nerve and retina cause loss of vision.

Glaucoma is moderately to extremely painful. The eye may be red and your dog may paw at it, or rub his or her head along the carpet. The eye may look cloudy due to swelling of the cornea and your dog will be very sensitive to light. The affected eye may seem larger, or appear to bulge out, relative to the other eye. Other more general signs of pain include loss of appetite and depression.
Glaucoma is an emergency. Treatment must be started as soon as possible if your dog's sight is to be saved. Irreversible damage to the retina and optic nerve occur within a few hours of significant elevation of the intraocular pressure.

How is ... diagnosed?:

Glaucoma is one of the conditions your veterinarian will suspect if your dog has a painful eye. It is diagnosed by measuring the intraocular pressure with a tonometer. This can usually be done with local anaesthetic drops placed in your dog's eye. To determine the type of glaucoma, gonioscopy is used to measure the iridocorneal angle.

How is ... treated?:

Preserving vision in an eye with glaucoma is difficult and requires aggressive medical and surgical therapy. Your veterinarian may choose to provide initial emergency medical therapy and refer you immediately to a larger veterinary centre.

Treatment depends on several factors - the type of glaucoma present, the degree of elevation of IOP, and the extent of visual impairment. Primary open angle glaucoma tends to be slower in onset and may, at least initially, be controlled by medical therapy (drugs) alone. With closed angle glaucoma, which is much more common, there is usually a sudden, rapid elevation in IOP. Ultimately, most forms of glaucoma require surgery.
If vision is present or has just recently been lost, a combination of medical and surgical therapy will be used to try and maintain your dog's sight . Aggressive medical therapy (meaning a combination of anti-glaucoma drugs administered frequently and monitored closely) is used to reduce IOP prior to surgery to prevent further damage to the eye. Some of these drugs will be used as well for additional minor IOP reductions following surgery. The aim of surgery in an eye that is still visual (or potentially visual) is to decrease the production of fluid within the eye, and to improve the drainage from the eye. There are a few different methods that a veterinary ophthalmologist can use to achieve this.
If the eye is irretrievably blind, glaucoma can be treated by removing the globe of the eye (enucleation). This will eliminate the pain for your dog. There are also procedures that can be done that preserve the globe such as placing a prosthesis.
Inherited glaucoma usually occurs in both eyes eventually. Your veterinarian will monitor the pressure in the other eye regularly, and discuss with you recognition of early signs of glaucoma. He or she may also recommend preventive medication for the unaffected eye.

For the veterinarian:

Because of the potential for elevated IOP to quickly cause irreversible damage to the visual structures of the eye, the timely diagnosis of glaucoma is very important. IOP should be measured in all red eyes for which the cause is not immediately obvious, and in eyes with unexplained pupillary abnormalities, corneal edema, or visual impairment, particularly if these signs occur in a dog that is of a breed with a predisposition to glaucoma. (See references below for a good discussion of accurate IOP measurement, as well as therapy).

Although the normal range of IOP varies (based on tonometer and other factors), generally a measurement of >25 mm Hg indicates glaucoma. An IOP of 50 mm Hg or more can lead to permanent optic nerve and retinal damage within hours if not relieved.

Breeding advice:

Animals of predisposed breeds should be screened for glaucoma before being used for breeding. Affected dogs and their close relatives should not be bred. Unfortunately, glaucoma does not generally become apparent until after breeding age has been reached, usually 3 years of age or greater.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Miller, P.E. 1995. Glaucoma. In J.D. Bonagura and R.W. Kirk (eds.). Kirk's Current Veterinary Therapy XII Small Animal Practice, p. 1265-1272. W.B. Saunders Co., Philadelphia

Slatter, D. 1990. Fundamentals of Veterinary Ophthalmology. W. B. Saunders Co., Philadelphia

Imperforate lacrimal punctum

roblib — Wed, 14 Apr 2010 15:54:07 +0000

What is ... ?:

Tears are produced normally to lubricate and cleanse the surface of the eye. The lacrimal punctum is the opening in the corner of the eye through which the tears drain into the nasolacrimal duct. If the lacrimal duct does not open at the punctum (ie. is imperforate), the tears overflow onto the face and, over time, there is rust-coloured staining of the coat in the corner of the eye. An imperforate lacrimal punctum is inherited in some breeds; however the punctum may become blocked in any animal due to inflammation or infectious disease.

How is ... inherited?:

The mode of inheritance is unknown.

What does ... mean to your dog & you?:

There is a chronic overflow of tears onto the face, in one or both eyes. In dogs with light coats, rust-coloured staining will develop over time. There are no other associated problems.

How is ... diagnosed?:

Your veterinarian will flush the nasolacrimal system to determine if an imperforate punctum is the cause of the excess tearing (called epiphora).

How is ... treated?:

Your veterinarian will identify where the punctum should open by flushing the nasolacrimal duct under general anaesthetic, and then make a small incision to open it.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Keratoconjunctivitis sicca (KCS) - "dry eye"

roblib — Wed, 14 Apr 2010 15:59:28 +0000

What is ... ?:

KCS or "dry eye" is an eye disease caused by abnormal tear production. The lacrimal glands produce the watery secretions that make up the bulk of the tears. A deficiency in this secretion causes KCS in small animals.

Normal tears are essential for the health and transparency of the cornea (the surface of the eye). Tears cleanse and lubricate the cornea, carry nutrients, and play a role in the control of infection and in healing. Deficient tear production as in KCS causes chronic irritation of the cornea and conjunctiva. Corneal ulcers and eventually corneal scarring occur, and blindness can result.
There is a predisposition to this condition in some breeds as listed below. KCS can also occur in any breed as a result of viral infection, inflammation, drug-related toxicity, or immune-mediated disease. There is an association between removal of a prolapsed nictitans gland ("cherry eye") and the development of KCS.

How is ... inherited?:

The mode of inheritance is not known.

What does ... mean to your dog & you?:

KCS may develop very quickly or more slowly, in one or both eyes. Commonly it is diagnosed in 1 eye first and develops in the other eye within several months. The extent of discomfort depends on the severity of the tear deficiency and how long it has been present. People with KCS say it feels like they have sand paper under their eyelids with every blink. Dogs show their discomfort by rubbing their eyes, squinting, and being sensitive to light. Your dog's eye(s) may be reddened and inflamed, or the cornea may appear dull and dry. There is commonly a thick mucousy discharge in the eye or in the area around the eye.

Problems associated with KCS include chronic or recurring irritation or infection of the conjunctiva and cornea, and corneal ulcers. These conditions are painful and, if KCS is untreated, over the long term the normally transparent cornea becomes thickened and scarred. Blood vessels and pigmented cells move in to the cornea because of the chronic inflammation, and blindness may result.

How is ... diagnosed?:

Your veterinarian may suspect KCS based on the kinds of clinical signs mentioned above, particularly in a breed with a predisposition to this disorder. KCS is confirmed by measuring your dog's tear production. Your veterinarian will also perform a fluoroscein dye test to check for corneal ulceration.

How is ... treated?:

The goals of treatment are to restore moisture to the eye and to treat conditions such as infection or ulceration that develop because of the lack of normal tears.

Tear stimulants and artificial tear replacements are used to treat KCS. Generally it will take a period of trial-and-error for your veterinarian to determine what is best for your dog. A response to tear stimulants may not occur for a few weeks or even longer, and during this time artificial tears must be used as well. Once tear production has been established, often the use of a tear stimulant once daily, or sometimes once every 2 days, will be sufficient to control KCS.
It is important to recognize that this treatment is not a cure for KCS but rather a way to manage a frustrating, painful, and potentially blinding condition. Clinical signs will slowly return If treatment is stopped.
When medical therapy as outlined above is unsuccessful, surgery can be done to transport one of the salivary ducts to provide moisture to the eye. This is generally less satisfactory.
FOR THE VETERINARIAN: Cyclosporine is the treatment of choice due to its efficiency at stimulating tear production, the need for fewer applications, and the lack of undesirable side effects with long term use. The time required to achieve sufficient tear production varies; usually a response is seen within a few weeks but several weeks may be required. Artificial tears should be supplied until tear production is established.

For the veterinarian:

A Schirmer tear test (STT) should be performed before the use of any drops or ointments in any dog presenting with ocular discharge, irritation, or corneal lesions. Normal STT values in the dog are 15 to 25 mm/minute. Dogs with exposed corneas due to conformation require relatively more tears so may show KCS even with marginal deficiencies.

Breeding advice:

Affected dogs should not be used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN

Resources:

Salisbury, M.A. 1995. Keratoconjuctivitis sicca. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1231-1239. W.B. Saunders Co., Toronto.

Lens luxation

roblib — Wed, 14 Apr 2010 16:17:56 +0000

What is ... ?:

With this disorder there is abnormal positioning of the lens within the eye. Normally the lens is suspended between the iris and the retina, held in position by the lens zonules and the adjacent vitreous (see diagram). There can be partial (sub-luxation) or complete displacement (luxation) of the lens from its normal site, either forward into the anterior chamber of the eye (in front of the pupil) or backward into the vitreous.

Forward (anterior) lens luxation in particular may cause an increase in the pressure within the eye (glaucoma), which if untreated leads to blindness.
Lens luxation may be primary (inherited), with certain breeds predisposed as listed below. Secondary luxation may occur in any breed as a result of trauma, inflammation, glaucoma or an intraocular tumour.

How is ... inherited?:

The mode of inheritance is not defined.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Inherited (primary) lens luxation occurs in young to middle-aged animals of 4 to 7 years. The lens usually displaces forward into the anterior chamber. In older animals, the lens displaces more easily backwards into the vitreous space.

A lens that displaces forward into the anterior chamber will often cause increased pressure within the eye leading to glaucoma. This is an emergency, as increased intraocular pressure can cause blindness within several hours. Your dog will experience intense pain and tearing of the eye, as well as reduced vision. With these signs, your dog should see your veterinarian immediately to prevent irreversible loss of vision.
Other signs of lens luxation are that your dog's eyes may appear asymmetrical to you or the affected eye may look cloudy. Sub-luxations and posterior luxations may ultimately result in glaucoma as well.
In predisposed breeds, lens luxation often occurs in both eyes at the same time, or in the second eye within a few months of the first.

How is ... diagnosed?:

With an anterior luxation, your dog may show intense pain (rubbing, pawing at the eye), tearing and visual impairment associated with glaucoma. Alternately, your dog may show no clinical signs associated with the lens luxation (usually a sub- or posterior luxation) and your veterinarian may observe an ocular abnormality during a routine physical examination. He/she will examine your dog's eye with an ophthalmoscope and measure the intraocular pressure. This can usually be done with local anaesthetic drops placed in your dog's eye.

How is ... treated?:

Treatment depends on the location of the lens (anterior or posterior), the presence or absence of acute glaucoma, and the potential for vision.

With sudden anterior lens luxation, your veterinarian will immediately start medical therapy for glaucoma. The lens should be surgically removed as soon as possible. If the intraocular pressure is elevated, then surgery is urgent to prevent permanent damage to the retina and optic nerve. Pressures over 50 mm Hg will cause such damage within hours.
For dogs with anterior lens luxation that have become blind, glaucoma can be treated by removing the globe of the eye (enucleation). This will eliminate the pain for your dog. There are also procedures that can be done that preserve the globe such as placing a prosthesis.
Posterior luxated lenses are difficult to remove surgically. As long as the lens can be maintained in that position, problems with vision are less likely. Long-term eyedrops can be used to keep the pupil small and the lens behind it.

For the veterinarian:

PHYSICAL EXAM: may see blepharospasm, epiphora, central corneal edema
OPHTHALMOSCOPIC EXAM: may see increased or decreased anterior chamber depth, iridodonesis, aphakic crescent, central corneal edema; with anterior displacement the IOP is generally elevated ( IOP of 50 mm Hg or more will lead to permanent optic nerve and retinal damage within hours if not relieved); IOP may be decreased due to uveitis caused by lens irritation.

Breeding advice:

Dogs that have experienced lens luxation should not be used for breeding. However this condition often does not occur before 4 to 7 years of age, making it difficult to identify affected dogs before they are used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Morgan, R.V. 1994. Ocular emergencies - part 2. A.C.V.I.M. - Proceedings of the 12th Annual Veterinary Medical Forum. p. 52-56.

Microphthalmia; ocular dysgenesis

roblib — Wed, 14 Apr 2010 16:38:28 +0000

What is ... ?:

Affected dogs have prominent third eyelids and small eyes which appear recessed in the eye socket (enophthalmos). A defect early in development results in the smaller than normal eye (microphthalmia).This is often associated with other eye abnormalities, including defects of the cornea, anterior chamber, lens and/or retina. Microphthalmia is also seen with coloboma - a cleft in a portion of the eye, particularly the iris.

Microphthalmia with multiple defects (ocular dysgenesis) is often seen in dogs with a merle hair coat with excessive amounts of white. The eyes are commonly different colours. Partial deafness may also be part of this syndrome. These dogs are frequently blind.

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How is ... inherited?:

In Doberman pinschers and miniature schnauzers, inheritance is autosomal recessive. The mode of inheritance has not been proven for other affected breeds. Microphthalmia with multiple defects (ocular dysgenesis) is a recessive trait in merle Australian shepherds.

What does ... mean to your dog & you?:

Microphthalmia may be associated with other minor or major eye abnormalities. Where the changes are mild, there is usually no visual impairment. With moderate microphthalmia, the eyeball fills about half of the opening. About 50% of these pups will be blind. Where the defect is severe, all of the pups are blind. In general, microphthalmia is evident as soon as a pup's eyes are opened.

Pups with microphthalmia with cataracts will usually have some visual impairment. The cataracts may be progressive resulting in a worsening of vision, or they may mature and be reabsorbed, resulting in improved vision. This is unpredictable. In the process of resorption, liquefied lens material may leak into the eye causing inflammation.
With their acute senses of smell and hearing, dogs can compensate very well for impaired vision. You may not realize the extent of your dog's vision loss, particularly in familiar surroundings. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as consistently as possible, introducing any necessary changes gradually, and being patient.

How is ... diagnosed?:

This condition is apparent in pups once their eyes have opened. Affected eyes are smaller than normally and appear recessed. The third eyelid will be more prominent. Your veterinarian will examine your dog's eyes thoroughly for other abnormalities. With ocular dysgenesis, vision is frequently impaired.

How is ... treated?:

There is no treatment for the structural defects. Complications that may develop, such as glaucoma, are treated as required.

For the veterinarian:

Ocular abnormalities that may be seen with ocular dysgenesis and merling with excessive white in the coat, include microphthalmia, microcornea, heterochromia irides, cataract, staphyloma, retinal detachment, irregular pupil, white to blue iris (albino), angle dysgenesis, iris coloboma, and blindness.

Anterior cleavage syndrome,or anterior ocular dysgenesis, has been seen in association with microphthalmia in Doberman pinschers and Saint Bernards. In addition to other ocular abnormalities as seen above, the anterior chamber, pupil and iridocorneal angle are not formed. The anterior uvea is continuous with the posterior cornea. Pups are blind.

Breeding advice:

Parents, normal-eyed siblings, and affected dogs should not be bred.

Merling is inherited as a dominant trait. Heterozygotes for merling have merle or dappled coats and occasional eye abnormalities. Homozygotes have predominantly white coats and frequent eye abnormalities including microphthalmia. Due to the association of multiple defects with coat colour, selection towards a white or albino coat or towards excessive white in a merled breed (ie selecting for homozygotes) should be avoided.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Optic nerve hypoplasia and micropapilla

roblib — Wed, 14 Apr 2010 16:54:51 +0000

What is ... ?:

Optic nerve hypoplasia is an uncommon defect in which the optic nerve fails to develop normally, leading to blindness. One or both eyes may be affected. Micropapilla refers to a smaller than normal optic disc, and is not associated with loss of sight.

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How is ... inherited?:

The mode of inheritance is unclear.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Depending on the degree of hypoplasia (underdevelopment), an eye may be partially or completely blind. Usually if only one eye is affected, your dog will compensate for the decreased vision to the point that you are unaware of any abnormality. You may notice that the pupils of your dog's eyes are different sizes - the pupil of the affected eye will be larger.

If both eyes are affected, your dog will have some loss of sight or will be blind.

How is ... diagnosed?:

This condition is suspected when a dog is visually impaired from birth. Based on clinical and ophthalmoscopic examination, your veterinarian will determine if optic nerve hypoplasia is the cause. This condition must be distinguished from micropapilla, a normal variation of optic disc appearance where the disc is smaller but vision is normal.

How is ... treated?:

There is no treatment. With their acute senses of smell and hearing, dogs can manage well despite reduced vision. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as consistently as possible, introducing any necessary changes gradually, and being patient.

For the veterinarian:

With unilateral involvement, clinically you will see ipsilateral mydriasis, blindness, and absence of menace reflex and of direct pupillary light reflex, with normal consensual reflex in affected eye following stimulation of normal eye. If both eyes are affected, there will be bilateral mydriasis, no menace response, and reduced or absent pupillary light reflexes.

Ophthalmoscopic examination reveals a variable reduction in optic disc size, with normal or tortuous -appearing retinal vessels. Optic nerve hypoplasia may be difficult to differentiate from micropapilla on a routine ophthalmoscopic screening examination.

Breeding advice:

Affected dogs and close relatives should not be used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The genetic connection. p 159-160. AAHA Press. Lakewood, Colorado. This reference contains a comprehensive list of breeds in which optic nerve hypoplasia or micropapilla have been seen. .

Pannus - chronic superficial keratitis

roblib — Wed, 14 Apr 2010 17:03:20 +0000

What is ... ?:

Pannus, or chronic superficial keratitis, is a condition of ongoing inflammation of the cornea (the surface of the eye). Pannus begins as a grayish haze. Gradually blood vessels and pigmented cells move into the normally transparent cornea. As the inflammatory changes spread across the cornea, vision is affected. The condition gradually worsens and usually affects both eyes.

In atypical pannus, the third eyelid is affected rather than the cornea. This is most common in German shepherds.
Pannus appears to be caused by an inappropriate response of the immune system. It occurs more frequently and is harder to control in dogs that live at high altitudes and/or are exposed to increased levels of ultraviolet radiation.

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How is ... inherited?:

The mode of inheritance is unknown.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

If untreated, the blood vessels and inflammatory cells will spread over your dog's normally transparent cornea, gradually darkening and scarring it, and causing visual impairment. This can occur slowly over months or years, or it can occur rapidly to involve the whole cornea within a few months. The condition does not appear to be painful.

Lifelong treatment is required to control this disorder (see below). Usually pannus can be well-controlled, although it is harder to control in dogs living at high altitudes (above 1500 metres). Sometimes lesions will worsen in periods of environmental irritation or increased ultraviolet exposure, or if medication is given irregularly.

How is ... diagnosed?:

Diagnosis is made based on the signalment (breed and history) and the typical changes in your dog's cornea.

How is ... treated?:

Usually pannus can be well-controlled. However treatment must be lifelong and consistent, or the lesions will return and worsen.

The goal of treatment is to prevent vision loss, or to return as much vision as possible if there is loss. This is done with the use of anti-inflammatory drops in the eye. Drugs used alone or in combination include corticosteroids and cyclosporin A. Your veterinarian will make specific treatment recommendations based on the severity of the changes to your dog's eyes, and the response to therapy. Usually therapy begins with 4 treatments a day. As the size of the area affected decreases, treatments will be decreased to the lowest frequency that controls the condition.
Once effective treatment is established, your veterinarian will evaluate any changes once or twice a year, or if you notice a worsening of the condition as may occur in periods of environmental irritation or increased ultraviolet exposure.

For the veterinarian:

You will see bilateral lesions consisting of vascularization, pigmentation, or a combination - usually starting in the temporal or inferiotemporal quadrant and progressing centrally. Atypical pannus may affect the nictitating membrane without affecting the cornea. The leading edge of the nictitans is depigmented and the palpebral surface is red and thickened. Treatment is similar to that for typical CSK.

Breeding advice:

Affected dogs should not be used for breeding. Breeding of close relatives should be avoided as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Roberts, S.M. 1995. Pannus. In J.D. Bonagura and R.W. Kirk (eds.). Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1245-1248. W.B. Saunders Co., Toronto. - This has good information on treatment, including for advanced or refractory lesions.

Persistent pupillary membranes (PPM)

roblib — Wed, 14 Apr 2010 17:06:28 +0000

What is ... ?:

Persistent pupillary membranes are strands of tissue in the eye. They are remnants of blood vessels which supplied nutrients to the developing lens of the eye before birth. Normally these strands are gone by 4 or 5 weeks of age.

Depending upon the location and extent of these strands, they may interfere with vision. They may bridge from iris to iris across the pupil, iris to cornea (may cause corneal opacities), or iris to lens (may cause cataracts), or they may form sheets of tissue in the anterior chamber of the eye. In many dogs these tissue remnants cause no problems.

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How is ... inherited?:

Inheritance is not defined.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Generally persistent pupillary membranes cause no problems. However if attached to the cornea or lens, the strands can cause opacities which may interfere with vision. The cataracts that can occur with PPM usually don't worsen.

How is ... diagnosed?:

PPM are seen in young dogs. You or your veterinarian may notice small white spots in your dog's eyes, or you may suspect that your dog's vision is impaired if the condition is severe. With an ophthalmoscope, your veterinarian will be able to see the membranous strands, and whether they adhere to the lens or cornea.

How is ... treated?:

There is no treatment for the membranes themselves and in most cases there are no associated problems. If there is significant edema or "bluing" of the cornea due to adhesions, hyperosmotic eyedrops may help. Surgery may be required if there are extensive cataracts.

Breeding advice:

This is a particularly common defect in basenjis. Affected dogs and their close relatives should not be used for breeding. Ideally, all basenjis, even those not obviously affected, should have careful ophthalmic examinations for PPM before their use in a breeding programme.

The defect is also significant in Welsh corgis (Pembroke and Cardigan), chow chows, and mastiffs. Affected dogs and their close relatives should not be used for breeding.
In other breeds, parents and siblings of affected dogs should be examined ophthalmoscopically. If close relatives are affected, breeding is discouraged. Where PPM appears to be an isolated incident, breeders may use their discretion.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Gelatt, K.N. 1991. Veterinary Ophthalmology. Lea and Febiger.