Effects of topical epinephrine on aqueous humor dynamics in the cat

The purpose of this study was to investigate, in cats, the effects of topic al epinephrine on aqueous humor dynamics as measured by the non-invasive me thod of fluorophotometry and by other methods. Measurements were carried ou t on 12 cats before and after one week of twice daily treatment with 2 % ep inephrine hydrochloride to one eye. Aqueous flow and outflow facility were determined using fluorophotometry. Uveoscleral outflow was calculated from these results and was evaluated with anterior chamber perfusion of FITC-dex tran. Outflow facility also was measured by tonography. Epinephrine-treated eyes, compared with their baseline values, showed a 31 % reduction in intr aocular pressure (P < 0.001), a 23 % reduction in aqueous flow (P < 0.05), a 60 % increase in fluorophotometric outflow facility (P < 0.05), and a 43 % increase in tonographic outflow facility (P < 0.05). Treated eyes, compar ed with contralateral control eyes, showed a 27 % reduction in IOP (P < 0.0 05), a 25 % reduction in aqueous flow (P < 0.005), a 38 % increase in fluor ophotometric outflow facility (P < 0.05), and a 34 % increase in tonographi c outflow facility. When evaluated by both fluorophotometry and FITC-dextra n tracer methods, epinephrine had no significant effect on uveoscleral outf low. It was concluded that, in cats treated with topical epinephrine twice daily for a week, a reduction in intraocular pressure is induced by an incr ease in outflow facility and decrease in aqueous flow. (C) 1999 Academic Pr ess.