The effect of trabeculectomy on variability of white-on-white perimetry

Purpose:To investigate changes in variability of white–on–white perimetry in patients undergoing trabeculectomy. Methods: 20 eyes of 20 patients who underwent trabeculectomy were enrolled in this retrospective study. Visual fields (full–threshold, 24 and 30 central degrees, Humphrey Field Analyzer) of preoperative and postoperative periods were analyzed in order to evaluate changes in short fluctuation (SF) and long–term fluctuation (LF) after trabeculectomy. The longest follow–up periods as possible were considered, provided that glaucoma was stable (as confirmed by intraocular pressure, optic nerve appearance and visual field). Postoperative data were also analyzed according to surgical success (complete, partial or no success). LF was defined as statistical variance. Results: Pre and postoperative follow–up was 1.4 ± 0.9 and 2.1 ± 1.2 years respectively. Preoperative SF was 3.2 ± 1.0 dB2, compared with 3.0 ± 1.1 dB2 postoperatively; the mean change in SF was –0.2 dB (P = 0.44). Preoperative LF was 4.97 ± 3.02 dB2, compared with 3.26 ± 2.53 dB2 postoperatively; the mean change in LF was 1.71 dB (P = 0.02). The group with complete surgical success showed a minor fluctuation in visual field repetition when compared with the other two groups (P = 0.05). Conclusions: The present study demonstrates a decrease in visual field LF in eyes undergoing trabeculectomy with complete surgical success. LF, together with visual field analysis of progression, could therefore be used as a parameter to state the efficacy of surgical procedures over time.