RESIO revisited: visual function assessment and cataract surgery in British Columbia.

BACKGROUND

Cataract surgery in a population with mild levels of functional impairment was studied in the Regional Evaluation of Surgical Indications and Outcomes (RESIO) project. The RESIO investigators assessed the overall visual function assessment (VFA) score before and after surgery. In this study we reanalysed available RESIO data to better understand the findings for individual VFA items in this patient population.

METHODS

We calculated effect sizes for longitudinal changes in each VFA item and for changes in overall VFA scores using the Mann-Whitney statistic. We considered effect sizes less than 0.3 as small, between 0.3 and 0.8 as moderate, and more than 0.8 as large. We compared differences in the individual VFA item scores before and after cataract surgery using a paired t test and Wilcoxon's signed-rank test.

RESULTS

Of the 32 surgeons originally involved in the RESIO project, 18 (60%) agreed to have the data for their patients reanalysed. We found pre- and postoperative VFA data for 709 cataract operations (mean age of patients 73.4 years [standard deviation 9.4 years]; 60.7% women). Of the 47 people with a perfect preoperative VFA score, 28 (59.6%) had a perfect score postoperatively, 13 (27.6%) had a score of 90 or better, 5 (10.6%) had a score of 87 to 90, and 1 (2.1%) had a score of 67. Among the 200 people with a preoperative VFA score of 90 to 99, postoperatively the VFA score improved for 146 (73.0%), remained the same for 43 (21.5%) and worsened for 11 (5.5%). The mean scores for all individual VFA items improved postoperatively. The largest improvements were noted for "driving during the day" (effect size 1.1), "self-care activities" (0.8), "driving during the night" (0.5), "doing fine handiwork" (0.5), "reading newspaper or book" (0.4) and "participating in religious activities" (0.4).

INTERPRETATION: The original conclusion from the RESIO project seems correct: based on VFA, the current threshold for cataract surgery in British Columbia is very low. Individual VFA items, particularly reading and night driving, are most strongly and consistently influenced by cataract surgery, regardless of overall VFA score. In the absence of visual acuity data, it is not possible to relate VFA to cataract surgical decision-making in British Columbia.