Six-year rate of visual field progression in the Laser in Glaucoma and Ocular Hypertension (LiGHT) Trial.

Abstract

Purpose: to compare the 6-year rate of visual field (VF) progression in the two arms of the Laser in Ocular Hypertension and Glaucoma Trial (LiGHT), comparing selective laser trabeculoplasty (SLT) and drops as first treatment in ocular hypertension (OHT) and open angle glaucoma (OAG).

Design: post-hoc analysis of data from randomized clinical trial SUBJECTS: patients with newly diagnosed OHT/OAG recruited in the LiGHT trial.

Methods: in each patient, we selected the better (baseline Mean Deviation, MD) eligible eye with at least 3 reliable VFs (false positive errors < 15%) over at least 6 months. We estimated the rate of MD progression using a published hierarchical linear mixed effect model (LMM), designed to increase precision by minimizing the effect of perimetric learning and test-retest noise. Secondary analyses were performed to assess: the differences in rate across baseline severity groups (OHT, mild OAG and moderate/severe OAG); the effect of glaucoma surgery and switch to SLT in the drops-first arm, by truncating the VF series; the effect of cataract and cataract surgery, by using the Mean Pattern Deviation (MPD) instead of the MD.

Main outcome measure: mean difference in the rate of VF MD progression between patients in the SLT-first and drops-first arm.

Results: Data from 710 eyes (482 with OAG, 354 in the SLT-first arm) were analysed. The two arms had similar baseline MD (p=0.7). The average intraocular pressure (IOP) during follow-up was 16.1 [14.2, 18.2] for the drops-first arm and 16.8 [14.6, 18.6] in the SLT-first arm (Median [Interquartile-range], p=0.057). The mean [95%-Credible interval] MD rate was -0.37 [-0.43, -0.31] dB/year in the drops-first arm and -0.26 [-0.31, -0.21] dB/year in the SLT-first arm (p = 0.007). When stratified by severity, this difference was significant only in mild OAG (p = 0.035, the largest sub-group). The secondary analyses largely confirmed the main results. The difference in MPD rate was also significantly slower in the SLT-first arm (p < 0.001).

Conclusions: First-line SLT was more effective than drops at preserving VF. SLT should be preferred as the first line of treatment in newly diagnosed OHT and OAG eyes.