All are true regarding retinitis pigmentosa EXCEPT

Ans) a (ERG is normal) Ref: kanski 6th ed p 663-667Retinitis pigmentosa is a group of retinal dystrophies initially affect-ing rods and then cones. Presents with nyctalopia (night blindness) often during third decade Clinical triad:1. arteriolar attenuation2. retinal bone spicule pigmentation3. waxy pallorERG shows reduced responses, EOG is subnormal Colour vision normal initiallyVisual field - annular mid peripheral scotoma which expands both cen-trally and peripherallyPrognosis- poor with eventual loss of central vision due to direct involve-ment of fovea by RP itself or maculopathyAtypical RP:Retinitis punctata albescens - characterised by scattered white dots Sector RP - involvement of one quadrant Pericentral RP - pigmentary changes start at the disc