The effect of long-term intraocular pressure reduction on the differential light sensitivity in glaucoma suspects

This study was undertaken to observe the effect on the differential light sensitivity in glaucoma suspects produced by a long-term reduction in intraocular pressure (IOP) with timolol maleate. The results are taken from an ongoing 6 year follow-up study of glaucoma suspects randomly selected for treatment and nontreatment. We present fine-grid meridional data, recorded every 4 months by automated perimetry, of all 46 patients (24 treated and 22 untreated) who completed the 6 year follow-up without developing localized visual field defects, acquired optic disc changes and whose IOP was not judged clinically dangerous during the follow-up. Methods of analyzing the profile sensitivity, the profile slope and the sensitivity of specific locations over the follow-up are described. The results show that the long-term fluctuation in differential light sensitivity in the two groups was not significantly different (P = 0.395) and that the sensitivity at most of the locations remained stable. The number of stable locations was not significantly different in the two groups (P = 0.412) and there was also no difference in the number of locations where the sensitivity appeared to decrease (P = 0.193) or increase (P = 0.540). Analysis of covariance showed no group difference in the profile sensitivity or the profile slope and that these variables remained stable in both groups over the 6 year period. Although the treated group maintained a consistently lower IOP than the untreated controls, our results showed that long-term pressure reduction with timolol in glaucoma suspects appeared not to influence the differential light sensitivity in the tested meridian.