Feline Retinal Hemorrhage
Retinal hemorrhage is bleeding into an area of the retina, the part of the eye that lies in the back of the eye and is responsible for receiving light. The retina acts like the film in a camera. Bleeding within the retina may originate from either the blood vessels of the retina or the choroid, which lies behind the retina. The bleeding may come from arteries, veins, or capillaries (the smallest of the blood vessels).
Retinal hemorrhages in cats often arise from some pathologic process either in the eye or somewhere else in the body. Therefore, in many cats, the presence of retinal hemorrhages 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 hemorrhage.
Retinal hemorrhages may involve one or both eyes. The age of onset varies widely and depends upon the ocular problem or underlying cause. Retinal hemorrhages are frequently associated with inflammation of the retina and choroid, and may be accompanied by detachment of the retina. See related article on retinal detachment in the cat.
Causes of Retinal Hemorrhage in Cats
Circulatory disorders that affect blood vessels may also cause retinal hemorrhages. Examples include high blood pressure (hypertension), too much circulating protein in the blood (hyperviscosity syndrome), weakening of the blood vessels from kidney disease, and sugar diabetes.
Hemorrhages may occur with clotting abnormalities of the blood. Disorders that affect blood clotting include decreased numbers of platelets in the blood, ingestion of rodents killed by warfarin poison, 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 retinal hemorrhages. Examples include feline infectious peritonitis virus, toxoplasmosis, fungal infections (histoplasmosis, cryptococcosis), and bacterial infections of the blood (septicemia).
Retinal hemorrhages are sometimes seen following surgery on the interior of the eye, radiation therapy to the head, or following certain manipulations of the eye.
Any tumor that arises in the retina or choroid, or that spreads to these tissues from another location (metastatic cancer) can potentially cause bleeding within the retina. Some examples include lymphosarcoma and metastatic tumors from the kidney, mammary glands and other organs.
Forceful trauma (such as from automobile accidents and falling from heights) is an uncommon cause of retinal hemorrhages. It is much more common for the blood vessels of the iris to bleed from such trauma, producing hyphema (blood in the front chamber of the eye). The presence of hyphema may not allow the retina to be examined, so it may be difficult to tell if retinal bleeding has also occurred. See related article on hyphema.
Choking injuries may result in retinal hemorrhages. Such injuries may occur with accidental hanging from catching collars on objects, during attacks from dogs, or when excessive force is applied to the neck.
What to Watch For
Unless retinal hemorrhages are severe or extensive there may be no ocular signs at all. Your veterinarian may only discover them when an eye examination is performed on your cat.
If only one eye is affected, the animal’s behavior may be normal. Vision can be lost in one eye without producing any signs.
If both eyes are severely affected or if the hemorrhages are accompanied by inflammation and/or retinal detachments, then signs of decreased vision may be evident, including dilated pupils, bumping into objects, reluctance to jump up on to objects, and reluctance to go outside.
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. It may look cloudy or red.
Retinal hemorrhages are not painful, but if the front tissues of the eye become inflamed, then squinting may occur.
If the bleeding is due to clotting problems with the blood, then there may be evidence of bleeding or bruising elsewhere in the body.
Other systemic signs may be detected if the hemorrhages are due to an underlying infection or widespread condition.
Diagnosis of Feline Retinal Hemorrhage
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 hemorrhages are obvious, while others can be difficult to see. Your veterinarian may refer your cat to a veterinary ophthalmologist for further evaluation using specialized instrumentation.
Once retinal hemorrhages are diagnosed in your cat, an extensive search is often 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
Possibly a heart and/or abdominal ultrasound
Treatment of Feline Retinal Hemorrhage
Treatment is usually directed at the underlying cause of the retinal hemorrhage. Depending on the physical condition of the patient, treatment options may include outpatient care or may necessitate hospitalization.
If the retinal hemorrhage 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
Chemotherapy for leukemias and other cancers
Vitamin K therapy and blood transfusions for clotting problems
Intravenous fluids for hyperviscosity and other circulatory disorders
Surgical removal of severely injured eyes or eyes with tumors
Administration of insulin for sugar diabetes
Administration of certain medications for thyroid gland diseases
If the retinal hemorrhages are not caused by infectious diseases, then systemic corticosteroids may be administered in an attempt to decrease any inflammation caused by the hemorrhages. It is important to note that the nonsteroidal anti-inflammatory medications (NSAIDs) are not used in this condition because they can alter platelet function and potentially make the hemorrhages worse.
Administer all medication as prescribed by your veterinarian. Return for follow up as directed to ensure that the hemorrhages and underlying condition are responding to treatment.
During the recovery period it is important to keep the cat quiet and confined, to avoid placing extensive force around the cat’s neck (replace collars with harnesses), to prevent violent shaking of the head so that further bleeding into the retina does not occur.
Small hemorrhages usually disappear within a few weeks to several months. Larger hemorrhages may take months or longer to resolve, and may predispose the eye to retinal detachment.