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Progressive retinal atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. Similar to retinitis pigmentosa in humans, [ 1 ] it is characterized by the bilateral degeneration of the retina , causing progressive vision loss culminating in blindness.
Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, [3] dilated pupils. Pupillary light reflexes are usually reduced but present; the slow phase mediated by melanopsin in retinal ganglion cells is retained.
The most common sign of CEA is the presence of an area of undeveloped choroid (appearing as a pale spot) lateral to the optic disc. The choroid is a collection of blood vessels supplying the retina. CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, retinal detachment, or intraocular hemorrhage.
Symptoms include sudden permanent blindness, dilated pupils, and loss of the pupillary light reflex. [63] Retinal detachment* is caused in dogs by genetic disorders such as retinal dysplasia or Collie eye anomaly, trauma, inflammation or cancer. Reattachment may occur spontaneously or with medical or surgical therapy.
Retinal detachment occurs with complete retinal dysplasia, and is accompanied by blindness in that eye. Cataracts or glaucoma can also occur secondary to retinal dysplasia. Other causes of retinal dysplasia in dogs include infection with canine adenovirus or canine herpesvirus , or radiation of the eye in newborns.
Symptoms include blurred vision in both eyes, but the onset may occur at a different time in each eye. There are yellow-white placoid lesions in the posterior pole at the level of the retinal pigment epithelium. Some suggest a genetic predisposition to the disease, while others postulate an abnormal immune response to a virus. [2]
Retinal tufts increase the risk of a retinal tear or a detached retina, although the risk is not high- 1% of tufts are thought to lead to retinal detachment. [2] [6] In addition if there is retinal thinning near a zonular traction tuft, there is an increased risk of retinal detachment. [5]
Patients on amiodarone with new visual symptoms should be evaluated by an ophthalmologist. Tobacco exposure, most commonly through pipe and cigar smoking, can cause optic neuropathy. Middle-aged or elderly men are often affected and present with painless, slowly progressive, color distortion and visual loss in both eyes.