Which of the parameter is decreased in Retinitis pigmentosa

* Retinitis Pigmentosa is a familial disease characterized by degeneration of photoreceptor with progressive night blindness and constriction of peripheral vision (may lead to functional blindness) * Docosahexanoic acid (DHA) comprises a small percentage (1-4%) of the total fatty acids of the membranes of most human tissues; however, it accounts for 30-40% of fatty acids in rod photoreceptor outer segments of the human retina. * Many patients with RP have lower plasma and red blood cell (RBC) lipid levels of the polyunsaturated fatty acid docosahexaenoic acid than non-affected individuals. The majority of patients with XLRP had 30-40% lower DHA levels in RBC lipids than normally sighted controls RP TRIAD:- * Includes fundus findings: Waxy pallor of the disc, aeriolar attenuation and bony corpuscular pigment clumps at the mid - peripheral retina.