Abstract
Abstract: :
Purpose: To determine whether the prostaglandin F2α analogue, travoprost, darkens iris color in rabbits with sympathetic denervation. Methods: Thirteen Dutch belted rabbits underwent bilateral superior cervical ganglionectomy. Starting the next day and for seven months thereafter, 0.004% travoprost was applied twice–daily to one eye and vehicle to the contralateral eye in a randomized, masked fashion. Color photographs of rabbit irides were taken at monthly intervals. Six masked observers rated paired photographs for differences in color using scores ranging from "0" for no obvious difference in iris color between paired eyes, to "3" for very certain of a color difference. The scores were analyzed using a random effects model. Scheffe multiple comparisons were made to compare scores by months. At seven months, protein and PGE2 levels were assessed in the aqueous humor, and tyrosinase in iris tissue. Values from right eyes were compared with left eyes by paired t–tests. Results: Based on an analysis of all observer scores over time, the travoprost–treated eyes were judged to be significantly (p=0.0007) darker than the contralateral vehicle–treated eyes. When evaluated month by month, eyes were judged to be darker at months 2 and 3 versus month 1 (p<0.05). There were no differences between eyes in protein or PGE2 levels in the aqueous humor, or tyrosinase in the iris. Conclusions: Travoprost darkens iris color in rabbit eyes with sympathetic denervation. In the same animal model, similar results have been found with latanoprost and unoprostone. Iris color darkening appears to be a class effect of PGF2α analogues.
Keywords: iris • pharmacology • intraocular pressure