All of the following are seen in retinitis pigmentosa except: September 2009
Ans. A: Prominent retinal vessels The condition is abiotrophic in nature (premature senility and death of tissue) and genetically determined. Autosomal recessive is the most common and is very severe. Autosomal dominant is benign and is symptomatic only in adult life. X-linked recessive is least common. It is also a very severe form. Degeneration of rods commences near the equator. Macular region is not affected until late in the disease. The symptoms of retinitis pigmentosa are characteristic, the most prominent being defective vision in the dusk (night blindness/nyctalopia). It is due to degeneration of rods, which are primarily responsible for vision in low illumination. The visual field show concentric reduction. In early cases a paial or complete annular/ring scotoma is found. As the disease progresses the field becomes gradually smaller until at last it is reduced to a restricted area around the fixation point (tubular vision).Hence person has difficulty in moving about. Initially the equatorial region is affected. Ophthalmoscopic findings in the affected zones shows the retina studded with small, jet black spots resembling bone corpuscles with a spidery outline. The retinal pigment epithelium becomes transparent so that the choroid vessels become visible and the fundus appears tessellated or tigroid. The retinal veins, never the aeries, often have a sheath of pigment for pa of their course. The retinal vessels becomes extremely attenuated and thread like. The disc exhibits the characteristics of primary optic atrophy. It is pale and have a wax like yellowish appearance and is often termed as 'consecutive optic atrophy' (Ganglion cells destroyed with degeneration of the axial cylinders and optic nerve is known as consecutive atrophy). Ocular associations of retinitis pigmentosa are myopia, chronic simple glaucoma. Systemic associations of retinitis pigmentosa are in the form of various syndromes: Laurence - Moon - Biedl syndrome - obesity, hypogonadism, polydactyly and mental retardation. Usher's syndrome - deaf mutism. Secondary retinitis pigmentosa due to infections like syphilis, mumps, German measles (rubella) and due to drug like chloroquine must be differentiated from primary retinitis pigmentosa. Treatment: is unsatisfactory Vasodilators - nicotinic acid. High doses of Vitamin A.
Prominent retinal vessels
Ring scotoma
Pigmentation around the retinal veins
Pale disc