Effect of Cataract Extraction on the Visual Field Decay Rate in Patients With Glaucoma

IMPORTANCE A visual field parameter that is resistant to cataract formation and extraction would help monitor glaucomatous visual field progression in patients with coexisting glaucoma and cataract. OBJECTIVE To evaluate the effect of cataract surgery on the slow and fast components of visual field decay in a group of patients with glaucoma. DESIGN, SETTING, AND PARTICIPANTS Retrospective, interventional, longitudinal study. Eighty-five eyes of 68 patients with open-angle glaucoma who had cataract extraction were included. All patients had 5 or more reliable visual field measurements before and after surgery. INTERVENTIONS A pointwise exponential regression was used to perform trend analysis on thresholds at visual field test locations before and after cataract surgery. The test locations were ranked according to the decay rate and were partitioned into slow and fast groups. MAIN OUTCOMES AND MEASURES The slow and fast visual field rate components were measured before and after cataract surgery and were compared. Linear regressions of the mean deviation and the visual field parameter were performed against time and were compared before and after surgery. RESULTS The mean (SD) mean deviation was -5.5 (5.1) dB before cataract surgery and -5.0 (4.9) dB after cataract surgery (P = .002). The mean (SD) Visual Field Index was 86.4% (13.5%) before cataract surgery and 86.6%(13.3%) after cataract surgery (P = .30). The mean (SD) slow component rate decreased from 0.48%(0.73%) per year before surgery to 0.26% (0.42%) per year after surgery (P = .04). No statistically significant difference was identified in the fast component mean (SD) rate per year before surgery (3.37%[4.05%]) vs per year after surgery (3.46%[3.56%]) (P = .29). CONCLUSIONS AND RELEVANCE Cataract progression seems to be the main determinant for the slow visual field rate component and does not change the fast visual field rate component. We conclude that the method used can help reduce the confounding effects of cataract progression and cataract extraction on measured perimetric progression in glaucoma.