The Advanced Glaucoma Intervention Study, 6: Effect of Cataract on Visual Field and Visual Acuity

OBJECTIVE: To investigate the effect of cataract on visual function and the role of cataract in explaining a race-treatment interaction in outcomes of glaucoma surgery. METHODS: The Advanced Glaucoma Intervention Study (AGIS) enrolled 332 black patients (451 eyes) and 249 white patients (325 eyes) with advanced glaucoma. Eyes were randomly assigned to an argon laser trabeculoplasty (ALT)-trabeculectomy-trabeculectomy sequence or a trabeculectomy-ALT-trabeculectomy sequence. From the AGIS experience with cataract surgery during follow-up, we estimated the expected change in visual function scores from before cataract surgery to after cataract surgery. Then, for eyes with cataract not removed, we used these estimates of expected change to adjust visual function scores for the presumed effects of cataract. In turn, we used the adjusted scores to obtain cataract-adjusted main outcome measures. MAIN OUTCOME MEASURES: Average percent of eyes with decrease of visual field (APDVF) and average percent of eyes with decrease of visual acuity (APDVA). RESULTS: Within the 2 months before cataract surgery, visual acuity was better in eyes of white patients than of black patients by an average of approximately 2 lines on the visual acuity test chart. Cataract surgery improved visual acuity and visual field defect scores, with the amounts of improvement greater when preoperative visual acuity was lower. Adjustments for cataract brought about the following relative reductions: for APDVF, a relative reduction of 5% to 11% in black patients and 9% to 11% in white patients; for APDVA, a relative reduction of 45% to 49% in black patients and 31% to 38% in white patients; and for the APDVF and APDVA race-treatment interactions, relative reductions of 25% and 45%, respectively. CONCLUSIONS: On average, visual function scores improved after cataract surgery. The findings of reduced race-treatment interactions after adjustment for cataract do not alter our earlier conclusion that the AGIS 7-year results support use of the ALT-trabeculectomy-trabeculectomy sequence for black patients and of the trabeculectomy-ALT-trabeculectomy sequence for white patients without life-threatening health problems. The choice of treatment should take into account individual patient characteristics and needs.