Retinal degeneration and disease can be a cause of blindness in dogs and cats. For instance, progressive retinal atrophy (PRA) is a hereditary condition that can strike middle-aged to older dogs and produce blindness over a period of several months to years. Breeds that are predisposed to this condition include Gordon setters, Irish setters, poodles, Norwegian elkhounds, Labrador retrievers, collies, cocker spaniels, and malamutes. Characterized by a slow degeneration of the receptor cells composing the retina, progressive retinal atrophy (PRA) in its early stages often leads to nightblindness in affected dogs. These dogs tend to fear or shy away from poorly lit areas. As progressive retinal atrophy (PRA) progresses, it eventually causes the pupils to remain dilated and fail to respond to light, causing complete blindness.
Retinal function may also be partially or completely lost due to underlying disease or injury. For example, glaucoma affecting an eye can place so much pressure on the blood vessels supplying the retina of that eye that secondary retinal degeneration results. Sudden acquired retinal degeneration (SARD) is another nonhereditary condition that can cause blindness in dogs, yet its exact cause remains a mystery. Interestingly, this disease is often accompanied by an increase in thirst and in appetite in those dogs so affected. Infectious diseases, such as ehrlichiosis and Rocky Mountain spotted fever, and fungi can also adversely affect the region of the retina where the optic nerve exits, leading to inflammation and subsequent loss of vision. In addition, neoplasms such as lymphosarcoma can infiltrate the retinas of dogs and cats and inhibit retinal function. Finally, trauma, immune-mediated diseases, and certain toxins can cause retinal injury and lead to blindness.
Diagnosis of retinal disease and degeneration is made using history, physical exam findings, and information obtained from an ophthalmic examination of the retinas themselves. In addition, an electroretinogram, which measures the electrical activity taking place within the retinas, will provide a definitive diagnosis of retinal degeneration and retinal blindness. If a disease condition such as glaucoma, infection, neoplasia, or toxicity is suspected, other diagnostic testing procedures specific to these conditions may be required as well to confirm a diagnosis.
Unfortunately, there are presently no known treatments for progressive retinal atrophy (PRA) and Sudden acquired retinal degeneration (SARD), and the prognosis remains grave for the restoration of sight in affected dogs. Other diseases involving the retina may respond favorably to treatments specific for the particular disorder; however, it
must be remembered that the longer such treatments are delayed or neglected, the greater the chances are of permanent loss of vision.
Retinal function may also be partially or completely lost due to underlying disease or injury. For example, glaucoma affecting an eye can place so much pressure on the blood vessels supplying the retina of that eye that secondary retinal degeneration results. Sudden acquired retinal degeneration (SARD) is another nonhereditary condition that can cause blindness in dogs, yet its exact cause remains a mystery. Interestingly, this disease is often accompanied by an increase in thirst and in appetite in those dogs so affected. Infectious diseases, such as ehrlichiosis and Rocky Mountain spotted fever, and fungi can also adversely affect the region of the retina where the optic nerve exits, leading to inflammation and subsequent loss of vision. In addition, neoplasms such as lymphosarcoma can infiltrate the retinas of dogs and cats and inhibit retinal function. Finally, trauma, immune-mediated diseases, and certain toxins can cause retinal injury and lead to blindness.
Diagnosis of retinal disease and degeneration is made using history, physical exam findings, and information obtained from an ophthalmic examination of the retinas themselves. In addition, an electroretinogram, which measures the electrical activity taking place within the retinas, will provide a definitive diagnosis of retinal degeneration and retinal blindness. If a disease condition such as glaucoma, infection, neoplasia, or toxicity is suspected, other diagnostic testing procedures specific to these conditions may be required as well to confirm a diagnosis.
Unfortunately, there are presently no known treatments for progressive retinal atrophy (PRA) and Sudden acquired retinal degeneration (SARD), and the prognosis remains grave for the restoration of sight in affected dogs. Other diseases involving the retina may respond favorably to treatments specific for the particular disorder; however, it
must be remembered that the longer such treatments are delayed or neglected, the greater the chances are of permanent loss of vision.
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