Earliest symptom of retinitis pigmentosa -
Ans. is 'b' i.e., Nyctalopia Clinical features of retinitis pigmentosao Symptoms are characteristics and depend on the type of retinitis pigmentosa : - Rod cone type: - It is the usual pattern. Rods are degenerated early and cones are involved late. Degeneration starts in a zone near the equator and gradually spreading anteriorly and posteriorly. The macular region is not affected until a late stage. The rods are responsible for the vision in dim light, dark adaptation, and peripheral vision, therefore, symptoms due to their degeneration are : -Nightblindness (or nyctalopia), i.e., defective vision in dim light, is the earliest feature.Defective dark adaptation (later)Loss of peripheral vision with preservation of central vision till late - Tubular (tunnel) vision.Mid-peripheral ring scotoma (annular scotoma) because the maximum density of rods occurs in mid-periphery.Ultimately central vision is also lost after many years.Cone-rod type : - Cones are degenerated early. As cones are responsible for vision in bright light, colour vision and central vision, the symptoms of this type of retinitis pigmentosa are reduction in central acuity, colour vision defect and defective vision in bright light. At least some peripheral vision is retained till very late.
Ring scotoma
Nyctalopia
Tubular vision
None
Retina