The ocular fundus is the back of the eye opposite the pupil and includes the portion of the white of the eye (sclera) that is in the back of the eye, the retina, the membrane between the retina and the sclera (the choroid), and the optic disk. Diseases of the ocular fundus may occur on their own or as a part of generalized diseases. Inherited abnormalities may be present at birth or appear later, and are important in the cause, development, and effect of diseases of the retina in cats. Trauma, metabolic disturbances, whole-body infections, tumors, blood abnormalities, high blood pressure, and nutritional deficiencies are possible underlying causes for diseases of the retina in cats.
Cats require a certain quantity of an amino acid, taurine, in their diet to prevent retinal disease and degeneration. All commercially prepared cat foods are now required to contain sufficient levels of taurine to prevent this condition, and it is rarely seen in cats kept as pets and fed a good-quality commercial diet formulated for cats.
Inherited Diseases of the Retina
Inherited abnormalities may be present at birth or appear later, and are important in the development of diseases of the retina in cats.
Abnormal Development of the Retina (Retinal Dysplasia)
An abnormal development of the retina called retinal dysplasia is present at birth and may arise from trauma, genetic defect, or damage occurring while in the womb. Viral infections of the mother (for example, panleukopenia), especially during early fetal development, can result in retinal dysplasia and other eye abnormalities in kittens.
Progressive Retinal Atrophy
Progressive retinal atrophy is the name for a group of diseases that cause degeneration of the retina. This includes inherited abnormalities of the light-sensitive layer of the retina. In Abyssinian cats, progressive retinal atrophy occurs as both abnormal development and degeneration. Night blindness is noted early and progresses to total blindness over periods of months to years. Cataracts can occur late in the course of progressive retinal atrophy and may make it difficult to detect the underlying disease of the retina. No effective therapy is available.
Inflammation of the Retina and Choroid (Chorioretinitis)
Inflammation of the retina and choroid (chorioretinitis) may result from a body-wide infection. In cats, infection may be associated with certain viruses (such as feline infectious peritonitis Feline Infectious Peritonitis (FIP) Feline infectious peritonitis (often called FIP) is a severe, usually fatal disease caused by a feline coronavirus. Coronaviruses are a family of viruses that chiefly cause respiratory infections... read more , feline leukemia virus Feline Panleukopenia Feline panleukopenia (also called feline infectious enteritis or feline distemper) is a highly contagious, often fatal, viral disease of cats. Kittens are affected most severely. Feline panleukopenia... read more , and feline immunodeficiency virus Immunodeficiencies Caused by Viruses Like people, cats can develop diseases and conditions that impair the function of their immune systems. Immune deficiency diseases have serious consequences and often lower the body’s defenses... read more ), toxoplasmosis, fungal diseases, parasites, bacterial infections, and tuberculosis. Unless the abnormalities are widespread or involve the optic nerve, there are often no signs. Therapy is directed at the underlying cause of disease.
It is important to be sure your pet receives regular, routine eye examinations. These examinations are important because they can often help diagnose many generalized diseases quickly and accurately, thus permitting early therapy.
When the retina is detached, it is separated from the back of the eye and from part of its blood supply, preventing it from functioning properly. In cats, detachment of the retina occurs with chorioretinitis associated with feline infectious peritonitis, feline leukemia, and high blood pressure.
The retina may become detached as a result of infection or inflammation. As a result, one pupil may be larger than the other.
Signs that the retina has become detached include excessive or prolonged dilation of the pupil, pupils of different sizes, loss of vision, and bleeding within the eye. Eye examinations need to be performed to confirm the diagnosis.
Detachments of the retina are treated medically with therapy directed at the primary disease or surgically to correct the detachment. Your veterinarian will select the treatment approach most appropriate for your cat’s condition. Retinal degeneration may be present in the reattached areas.