Feline Retinal Detachments
Retinal detachment is the separation of the retina, the innermost layer of the back of eye from the underlying pigmented epithelium and choroid. The choroid is a darkly colored, vascular layer that furnishes nutrition to the retina. Retinal detachment in cats 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 cats, 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 cat than the actual detachment.
Congenital Causes of Retinal Detachment in Cats
It is rare for cats to be born with retinal detachments or to develop them shortly after birth. There are instances, however, in which these types of detachments can occur:
Severe retinal dysplasia or folding of the retina, often associated with infections with feline panleukopenia during the pregnancy
Multiple ocular defects caused by poor nutrition, exposure to radiation, or other serious infections during the pregnancy
Circulatory Causes of Retinal Detachment in Cats
High blood pressure (systemic hypertension) is the most common cause of retinal detachments in the cat. It is a disease of older cats. 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 cats are chronic kidney disease 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 include feline infectious peritonitis virus and a particular form of leukemia or lymphoma of white blood cells.
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 over production of white blood cells (leukemias), over production 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, decreased vitamin K levels in the body, liver disease, leukemia and cancer of the bone marrow, etc.
Infectious Causes of Retinal Detachment in Cats
Any infection that causes inflammation of the retina or underlying choroid can potentially cause a retinal detachment. Examples include fungal infections such as histoplasmosis and cryptococcosis, parasitic infestations such as larval migrans, and bacterial infections of the blood (septicemia).
Fortunately detachment of the retina is an uncommon complication of these conditions.
Degenerative Causes of Retinal Detachment in Cats
In the final stages of retinal degeneration a detachment may develop. Retinal degeneration is uncommon in the cat, but can occur with a dietary deficiency of taurine (an amino acid) and with inherited degenerations of the retina. See related article on Progressive Retinal Degeneration in cats.
Retinal detachments may sometimes be seen in cases of chronic glaucoma after the retina has deteriorated.
Toxic Causes of Retinal Detachment in Cats
Ingestion of rodents killed by warfarin-type poisons can cause bleeding in the back of the eye and possible detachment of the retina.
Toxic causes include reactions to drugs such as griseofulvin.
Ingestion of antifreeze (ethylene glycol) rarely causes retinal detachments.
Cancerous Causes of Retinal Detachment in Cats
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, 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.
Traumatic Causes of Retinal Detachment in Cats
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 cats with detachments due to hypertension, the onset of blindness is usually very rapid (within 1 to 3 days) and 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 Feline Retinal Detachments
A complete history and physical examination 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 cat to a veterinary ophthalmologist for further evaluation using specialized instrumentation.
Once a retinal detachment is diagnosed in your cat, 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)
Possibly a heart and/or abdominal ultrasound
Treatment of Feline Retinal Detachments
Therapy must be instituted as early in the disease process as possible, or the detached retina will deteriorate and the cat 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 therapy for certain infections
Chemotherapy for leukemias and other cancers
Vitamin K therapy
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.
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 guarded. Although some retinas reattach once therapy has been started, it is rare for vision to return. Because the detachment may also signify the presence of a serious illness in the cat, the prognosis for the cat’s overall health may also be poor to guarded.
In general, high blood pressure is a very treatable disease and cats may remain in reasonably in 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 cats adjust very well to their blindness.
Other diseases may not respond to therapy as well, and the life of the cat may be shortened.
Supervision of irreversibly blind cats is important.
They should only be allowed outside on a leash, or in a confined area under direct supervision.
Place barriers across staircases, over hot tubs and around pools. Do not allow the cat out onto balconies.
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 cat will memorize a familiar (stable) environment in a relatively short time.
Purchase toys that contain bells or other noisemakers to encourage and help cats to play.