The effect of ocular pigmentation on intraocular pressure response to timolol

The one-hour intraocular pressure (IOP) response to topical ocularly applied timolol was studied in darkly and lightly pigmented eyes. One drop of 0.25% 1-timolol was applied to one eye of ten subjects with brown and ten subjects with blue iris color. In the treated and untreated eyes with blue iris color the IOP fell significantly from the baseline value, whereas no pressure reduction was obtained either in the treated or untreated eyes with brown iris color. Beta-blocking agents are known to accumulate in pigment-containing ocular structures. The lack of a one-hour pressure response to timolol in darkly pigmented eyes observed in our study may refer to the reduction of 1-timolol in the biophase due to excessive pigment binding.