<prompt> Colourblindess is caused byChloroquineEthambutolDigitailsPZM  <response>: Ans. b Ethambutol. Ref. Katzung 12thChapter 47Hypersensitivity to ethambutol is rare. The most common serious adverse event is retrobulbar neuritis, resulting in loss of visual acuity and red-green color blindness. This dose-related adverse effect is more likely to occur at dosages of 25 mgkgd continued for several months. At 15 mgkgd or less, visual disturbances are very rare. Periodic visual acuity testing is desirable if the 25 mgkgd dosage is used. Ethambutol is relatively contraindicated in children too young to permit assessment of visual acuity and red-green color discrimination.Drugs causing color vision alterationDrugs causing cataractDrugs causing retinopathyBarbituratesBusulfanChloroquineDigoxin yellow visionSteroidPhenothiazidesEthambutol red-green blindnessPhenothiazidesDEC anti-filarialSildenafil citrate blue-green blindnessMiotics Thioridazone, thiazidesGold SulfonamidesChloroquine SYSTEMIC DRUGS:ADVERSE OCULAR EFFECTSOxygen Retinopathy of prematurity.0Digitalis Disturbances of color vision yellow vision, scotomas, photopsia.Quinidine Optic neuritis rare.Thiazides Xanthopsia yellow vision, myopia.Carbonic anhydrase inhibitors Ocular hypotony, transient myopia.Amiodarone Corneal deposits.Anticholinergic agents Risk of angle closure glaucoma due to mydriasis. Blurring of vision due to cycloplegia.Barbiturates Extraocular muscle palsies with diplopia, ptosis, cortical blindness.Chloral hydrate Diplopia, ptosis, miosis.Phenothiazines Deposits of pigment in conjunctiva, cornea, lens and retina. Oculogyric crises.Amphetamines Widening of palpebral fissure. Dilation of pupil, paralysis of ciliary muscle with loss of accommodation.Monoamine oxidase MAO inhibitors Nystagmus, extraocular muscle palsies, optic atrophy.Tricyclic agents Dilation of pupil risk of angle closure glaucoma0, cycloplegia.Phenytoin Nystagmus, diplopia,0 ptosis, slight blurring of vision rare.Neostigmine Nystagmus, miosis.Morphine Miosis.Haloperidol Capsular cataract.Lithium carbonate Exophthalmos, oculogyric crisis.Diazepam Nystagmus.Corticosteroids Cataract posterior subcapsular, local immunologic suppression, causing susceptibility to viral herpes simplex, bacterial, and fungal infections; steroid induced glaucomaFemale sex hormones Retinal artery occlusion, retinal vein occlusion, papilledema, ocular palsies with diplopia, nystagmus, optic neuropathy, retinal vasculitis, scotomas, migraine, mydriasis and cycloplegia, and macular edema.Chloramphenicol Optic neuritis and atrophy.Rifabutin Uveitis.Streptomycin Optic neuritis.Tetracycline Pseudotumor cerebri, transient myopiaChloroquine Macular changes, central scotomas, pigmentary degeneration of the retina, chloroquine keratopathy, ocular palsies, ptosis, ERG depression.lodochlorhydroxyquin Optic atrophy.Sulfonamides Stevens Johnson syndrome.Ethambutol Optic neuritis and atrophy.Isoniazid Optic neuritis and atrophy color blindness.Gold salts Deposits in the cornea and conjunctiva.Lead Optic atrophy, papilledema, ocular palsies.Penicillamine Ocular pemphigoid, optic neuritis, ocular myasthenia.Chlorpropamide Transient change in refractive error, diplopia, Stevens Johnson syndrome.Vitamin A Papilledema, retinal hemorrhages, loss of eyebrows and eyelashes, nystagmus, diplopia, blurring of vision.Vitamin D Band shaped keratopathy.Salicylates Nystagmus, retinal hemorrhages, cortical blindness rare.Indomethacin Corneal deposits.Phenylbutazone Retinal hemorrhages 