<prompt> Tobacco amblyopia is due to:CyanideNicotineDinitrobenzeneCarbon disulphide  <response>: Ans: a Cyanide Ref: AK Khurana, 3 ed, p. 282; 4th ed, p. 296Tobacco amblyopia is due to cyanide.Tobacco amblyopiaEtiology:Heavy smokers, heavy drinkers a diet deficient in proteins vitamin B12CF:BL gradually progressive loss of visionBL centrocaecal scotomaBRIDGE Photoretinitis is due to Infrared raysSnow blindness photoophthalmia are due to UV rayFundus examination: Temporal pallor of optic disc normal optic discExcessive tobacco smoking: Decrease cyanide detoxification due to deficiency of sulphur rich proteinsExcess cyanide in blood - degeneration of ganglion cells - degeneration of papillomacular nerve bundle-atoxic amblyopiaTreatment:1. Cessation of smoking2. Inj. Hydroxycobalamine 1000 ug IM weekly for 10 weeks3. Health care nutritionCauses of centrocaecal scotoma:Ring scotoma;Lebers ischemic optic neuropathyVitB12 deficiencyTobacco amblyopiaMyopiaRetinitis pigmentosaPrimary open angle glaucomaPapilltisSarcoidosisLeukaemiaTubular vision;Retinitis pigmentosaPOAGCentral scotoma:Relative positive scotoma:RB neuritisEthambutolMacular hole; cyst degenerationCentral serous retinopathyPhotoretinitis 