Progressive Loss of Retinal Ganglion Cell Function Is Hindered with IOP-Lowering Treatment in Early Glaucoma

Abstract

To investigate progressive changes of retinal ganglion cell (RGC) function in glaucoma suspects before and after IOP-lowering treatment. The authors retrospectively analyzed pattern electroretinograms (PERG) recorded twice a year in 32 glaucoma suspects over at least 6 years. Fifteen patients (28 eyes in the study group) received IOP-lowering treatment at intermediate points during the follow-up, thereby generating a break point between the untreated period and the treated period. Seventeen patients (31 eyes in the control group) were not treated; a break point in the follow-up period was randomly assigned. To assess the effect of treatment, linear regression slopes of PERG amplitude were calculated for periods before and after the break point, and compared both within and between groups. Linear mixed models applied to raw PERG amplitudes recorded over the entire follow-up period were also calculated. Before the break point, slopes had a similar negative trend in both groups, whereas after the break point the slope became shallower in the treated group (P = 0.002). The linear mixed model revealed an interaction between groups, period relative to break point, and segment duration (P = 0.001). Both analyses agreed that after the break point, the rate of PERG amplitude decline slowed in treated eyes by 0.013-0.019 μV/year compared with the untreated eyes. Mean IOPs measured before and after break point were similar in control eyes (14.8 ± 3.20 vs. 14.8 ± 3.14 mm Hg) but different in treated eyes (16.84 ± 3.96 vs. 14.8 ± 3.24 mm Hg; P < 0.001). Progressive loss of RGC function in early glaucoma may be alleviated after IOP lowering, as measured by PERG.