This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro-Ophthalmology, Subject name: Ophthalmology
[{'content': 'Tobacco amblyopia is due to: \nSelect and explain. \nA. Cyanide, B. Nicotine, C. Dinitrobenzene, D. Carbon disulphide', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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 B12C/F:B/L gradually progressive loss of visionB/L 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', 'role': 'assistant'}]