Purpose: This study was to determine the role of changes in refractive error, contrast sensitivity, and corneal topography in transient changes in visual function following trabeculectomy.
Methods: We performed a prospective study evaluating these factors in 13 consecutive patients undergoing a standardized trabeculectomy. Preoperatively, and at 1, 4, and 12 weeks postoperatively, we measured best-corrected visual acuity, refractive error, and contrast sensitivity and analyzed computerized video-keratographic studies including estimated corneal visual acuity.
Results: One week postoperatively, best-corrected visual acuity decreased at least one line in 8 of 13 patients, whereas no eyes had decreased contrast sensitivity. Mean central corneal astigmatism increased 1.4 diopters along the surgical meridian. By 12 weeks, visual acuity returned to preoperative levels in all patients and the corneal topographic changes returned to within 1 diopter of preoperative values in 12 of 13 patients. Postoperative changes in estimated corneal visual acuity were similar to those in best-corrected visual acuity with no statistically significant difference.
Conclusions: Corneal topographic changes appear to contribute to visual acuity reduction following trabeculectomy. In most cases this is transient with return to preoperative topography within 12 weeks.