<prompt> Which of the following mydriatics has the shortest duration of action?AtropineHomatropineCyclopentolateTropicamide  <response>: Ans. is d i.e., Tropicamide Following table enumerates the salient features mydriatic durgs:Salient features of common cycloplegic and mydriatic drugsSI. NoName of the drugAge of the patient when indicatedDasage of instillationPeak effectTime of performing retinoscopyDuration of actionPeriod of postcycloplegic testTonus allowance1.Atropine sulphate 1 ointment 5 yearTDS x day2-3 days 4th day10-20 daysAfter 3 weeks of retinoscopyID2.Homatropine hydrobromide 2 drops5-6 yearsOne drop every 10 min. for 6 times60-90 rainAfter 90 min. of instillation of first drop48-72 hoursAfter3days of retinoscopy0.5D3.Cyclopentolate hydrochloride 1 drops8-20 yearsOne drop every 15 min. for 3 times80-90 minAfter 90 min. of instillation of first drop6-18 hoursAfter 3 days of retinoscopy0.75D4.Tropicamide 0.5, 1 dropsNot used as cycloplegic for retinoscopy; used only as mydriaticOne drop every 15 min 15 3 to 4 times20-40 min.-4-6 hours--5.Phenyephrine 5, 10 dropsUsed only as mydriatic alone or in combination with tropicamideOne drop every 15 min. for 3 to 4 times30-40 min-4-6 hours-- Tropicamide has has the shortest duration of action of 4 - 6 hours. 