Reversal of tropicamide mydriasis with single instillations of pilocarpine can induce substantial pseudo-myopia in young adults.

Author(s): Gilmartin B, Amer AC, Ingleby S

Affiliation(s): Department of Vision Sciences, Aston University, Birmingham, UK.

Publication date & source: 1995-09, Ophthalmic Physiol Opt., 15(5):475-9.

Publication type: Clinical Trial; Randomized Controlled Trial

Pupillary dilation for diagnostic purpose has become an increasingly common procedure in UK optometry in recent years and the consensus seems currently to militate against the routine use of miotics; an eye that is judged safe to dilate is thought to be at minimal risk during the natural recovery phase to normal pupil size. Nevertheless, the optometrist does, on occasion, need to consider whether there might be some advantage in minimising the sometimes debilitating effects of cycloplegia and mydriasis produced in young adults by tropicamide. In this context we compare the effects of single instillations of two miotic agents: the alpha-adrenoceptor antagonist thymoxamine HCl (0.5%), and the parasympathomimetic pilocarpine HCl (1 and 2%). Tropicamide was used to induce mydriasis in a group of 12 volunteer student subjects aged 20-26 years (7 males, 5 female; mean 21.67 years) selected to provide low (L; n = 4), medium (M; n = 4) and high (H; n = 4) iris pigment levels. Measurements of pupil diameter (Brocca pupillometer), Snellen visual acuity and accommodative amplitude (near point rule) were made every 3 min over a 90 min recording period for 4 trials: (1) a control condition whereby a miotic was not employed; (2) thymoxamine HCl 0.5% was instilled after 30 min; (3) and (4) pilocarpine 1% and 2% was instilled after 30 min, respectively. Tropicamide induced a mean increase in pupil area from 25 to 50 mm2 after 22 min which was generally sustained over the 90 min period and was enhanced for the lower pigment groups.(ABSTRACT TRUNCATED AT 250 WORDS)