Overview of Canine Retinal Detachment
Retinal detachment is the separation of the retina, the innermost tunic layer of the back of the eye, from the underlying pigmented epithelium and choroid. The choroid is the darkly colored, vascular layer that furnishes nutrition to the retina. Retinal detachment in dogs occurs most often from the accumulation of fluid under the retina, due to some pathologic process either in the eye or somewhere else in the body. Therefore, in most dogs, the presence of a retinal detachment is often a sign of a serious underlying disease. The underlying disease may be more of a threat to the health of the dog than the actual detachment.
Causes of Retinal Detachment in Dogs
Retinal detachments can occur in one or both eyes. The age of onset varies widely and depends upon the underlying cause or ocular problem.
It is uncommon for dogs to be born with retinal detachments, but sometimes detachments can develop in the first few months of life. These types of detachments are usually associated with severe, inherited birth defects of the eye, such as the following:
Severe retinal dysplasia or folding of the retina; sometimes also associated with skeletal deformities in large breed dogs
Collie eye anomaly with defects of the retina, choroid, and sclera in the back of the eye
Multiple ocular defects caused by poor nutrition, exposure to radiation, or other serious infections during the pregnancy
Inherited multiple ocular defects, especially those associated with excessive white coat coloring
High blood pressure (systemic hypertension) is a potential cause of retinal detachments in older dogs. High blood pressure results in fluid leakage and bleeding from blood vessels of the retina and under the retina. As fluid accumulates under the retina, the retina is pushed away from the underlying pigmented epithelium and a detachment develops.
The most common causes of hypertension in older dogs are chronic kidney disease and hyperadrenocorticism, which is too much steroid hormone output from the adrenal gland.
Rare causes include tumors of the adrenal glands and hyperthyroidism, which is too much hormone output from the thyroid gland.
Hyperviscosity syndrome can also cause retinal detachments. With hyperviscosity syndrome there is too much circulating protein in the blood and the blood becomes very thick. It causes the blood to act almost like sludge in the small blood vessels, and they can rupture or leak. Diseases that cause overproduction of protein in the blood usually involve tumors of the white blood cells that make serum proteins, such as lymphoma or multiple myeloma.
Blood can also become too thick and cause circulatory problems within the retina when there are increased numbers of cells in the blood. This can occur with overproduction of white blood cells (leukemias), overproduction of red blood cells (polycythemia), and excessive blood transfusion.
Poor clotting of the blood can result in hemorrhaging from the retinal or choroidal blood vessels and possible retinal detachment. Disorders that affect blood clotting include decreased numbers of platelets in the blood, inherited clotting disorders (hemophilia), decreased vitamin K levels in the body, liver disease, leukemia, and other cancers of the bone marrow.
Any infection that causes inflammation of the retina or underlying choroid can potentially cause a retinal detachment.
Examples include fungal infections such as blastomycosis, histoplasmosis, cryptococcosis and coccidiodomycosis; parasitic infestations such as larval migrans; infection with the blue-green algae called protothecosis; and certain bacterial infections, such as infections of the blood (septicemia).
Uveodermatologic syndrome, which is a rare disease of Oriental breeds of dogs and Arctic sled dogs, can cause retinal detachments. In this bizarre disease the darkly pigmented tissues of the body (skin, hair, eyes, lips) are attacked by the immune system and the pigment disappears.
Other immune causes of inflammation of the retina and choroid, especially in large breed dogs, can result in retinal detachments.
Systemic lupus erythematosus, which is an immune disorder that targets multiple organs (skin, kidneys, eyes), can rarely cause retinal detachments.
In the final stages of retinal degeneration a detachment may develop. Retinal degeneration occurs as an inherited condition in many breeds of dogs. See related article on Progressive Retinal Degeneration in dogs.
Retinal detachments may sometimes be seen in cases of chronic glaucoma, after the retina has deteriorated.
Retinal detachments may also be a long-term complication of surgery performed within the eye, such as after cataract extraction and removal of luxated (dislocated) lenses.
The shih tzu dog has an inherited tendency to develop retinal tears that can then progress to retinal detachments. The underlying mechanism of this disorder is unknown.
Ingestion of antifreeze (ethylene glycol) rarely causes retinal detachments.
Reactions to drugs such as sulfa products may cause enough fluid accumulation under the retina to produce a detachment.
Any tumor that arises in the retina or choroid, or that spreads to these tissues from another location (metastatic cancer) can cause a retinal detachment.
Some examples of these tumors include lymphosarcoma, melanoma, and metastatic tumors from the kidney, mammary glands and other organs.
Rarely, tumors of the optic nerve (nerve that leads from the retina to the brain) can cause a retinal detachment.
Penetrating injury or foreign body
Blunt trauma with inflammation or hemorrhage
What to Watch For
Blindness or reduced vision. The severity of vision loss is related to the extent of retinal detachment. If only one eye is affected, the animal’s behavior may be normal. The onset of blindness can be gradual or rapid. In dogs with detachments due to immune diseases or infections, the onset of blindness is usually very rapid (within 1 to 3 days) and often involves both eyes.
Dilated pupils with slow or no pupillary light reflex. Dilation of the pupils is one of the first and most obvious signs of retinal detachment. The pupil will open up as the eye loses its sight.
Possibly visible hemorrhage or discoloration of the front part of the eye. If blood from the back of the eye moves forward, or if the front portion of the eye becomes inflamed, then the appearance of the eye may become altered.
Diagnosis of Retinal Detachment in Dogs
A complete history and physical examination of your dog are important to document the onset and progression of any eye signs and systemic abnormalities.
A thorough ophthalmic examination is indicated. Some retinal detachments are easily identified, while others can be difficult to see. Your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation using specialized instrumentation.
Once a retinal detachment is diagnosed in your dog, then an extensive search is required to identify any underlying diseases. Tests to be considered include the following:
Complete blood count (CBC)
Measure of arterial blood pressure
Thyroid hormone assays
Blood clotting tests
X-rays of the chest and abdomen
Blood tests for infectious diseases
Serum protein assays, especially separating and characterizing proteins (electrophoresis)
Ocular ultrasound. Possibly a heart and/or abdominal ultrasound
Cerebrospinal fluid (CSF) tap
Possibly collection of fluid from the vitreous chamber in blind eyes suspected to be infected
Treatment of Retinal Detachment in Dogs
Therapy must be instituted as early in the disease process as possible, or the detached retina will deteriorate and the dog will be permanently blind. Treatment is usually directed at the underlying cause of the retinal detachment. The detachment itself is very difficult to treat. Depending on the physical condition of the patient, treatment options may include outpatient care or may necessitate hospitalization.
If the detachment is due to high blood pressure, then medications are instituted to lower the blood pressure. As the blood pressure is being controlled, systemic anti-inflammatory medications may be used to try to decrease the damage done to the retina.
Specific therapy for the underlying condition can include the following, depending upon the underlying cause:
Antibiotic and anti-fungal therapy for certain infections
Systemic corticosteroids for immune diseases
Chemotherapy for leukemias and other cancers
Vitamin K therapy and blood transfusions for clotting problems
Intravenous fluids for hyperviscosity and other circulatory disorders
Administration of antidotes for antifreeze toxicity
Surgical removal of severely injured eyes or eyes with tumors
Some types of retinal detachments are not treatable. Examples include the congenital detachments and detachments associated with degeneration of the retina.
Surgery or laser therapy may be tried for partial detachments that arise after intraocular surgery, or for retinal tears that occur in shih tzus and other dogs.
Home Care for Dogs with Retinal Detachment
Pets with recent onset of blindness should be evaluated by your veterinarian as soon as possible. Minimize stress and injury by confining your pet to a safe area until the cause of the problem is determined.
Administer all medication and return for follow-up examinations as directed by your veterinarian. Prognosis for return of vision is poor to guarded. Although some retinas reattach once therapy has been started, return of vision is uncertain. Because the detachment may also signify the presence of a serious illness in the dog, the prognosis for the dog’s overall health may also be poor to guarded.
In general, high blood pressure is a very treatable disease and dogs may remain in reasonably good health. They may be blind, however. In the event that vision cannot be saved, understand that such vision loss is not life threatening and the vast majority of dogs adjust very well to their blindness.
Some of the immune diseases also respond favorably to therapy and the retinas may reattach. In these cases, therapy must often be continued for long periods of time to control the disease. Other diseases may not respond to therapy as well, and the life of the dog may be shortened.
Retinal detachments caused by fungal infections may not respond well to treatment because the drugs may not get into the eye effectively. Although the drugs may cure the disease elsewhere in the body, the eye may be lost.
Supervision of irreversibly blind dogs is important:
They should only be allowed outside on a leash, or in a confined area under direct supervision. Place barriers across stair, over hot tubs and around pools.
Restrict activity on balconies so that small dogs cannot fall through the space between the guardrails and large dogs cannot unwittingly jump off the balcony. Fence open decks so that the dog cannot fall off.
Establish a known location for the food and water bowls and guide your pet to them if necessary.
Avoid changing the location of the furniture and leaving chairs or other objects out of place in the house. Your dog will memorize a familiar (stable) environment in a relatively short time.
Purchase toys and balls that contain bells or other noisemakers to encourage and help dogs to play.