<prompt> Which of the parameter is decreased in Retinitis pigmentosaArachidonic acidDocosahexanoic acidTrielonic acidThromboxane  <response>: 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. 