Changes of Visual Functions and Ocular Parameters following Trabeculectomy with Mitomycin C

Kook, M S; Kim, H B

Abstract

We studied to find changes in ocular structures and visual functions following trabeculectomy with mitomycin C and to note the association between structural changes and the visual functions. We evaluated corneal astigmatism, axial length, corneal topography as structural changes in 11 eyes of 9 patients who were followed up for at least 1 year after trabeculectomy with mitomycin C, and corrected visual acuity, and contrast sensitivity as visual functions in 8 eyes of 8 patients whose preoperative corrected visual acuity was 0.4 or better. Keratometry showed with-the-rule astigmatic changes up to 3 months postoperatively, and then against-the-rule astigmatic changes were followed through 12 months postoperatively by vector analysis. In corneal topography, corneal steepening along the surgical meridian occurred in all patients. Mean axial length preoperatively was 24.3 mm, and 23.2 mm at 1 week, 22.9 mm at 1 month, 23.2 mmat 3 months, 23.4 mm at 6 months, and 23.4 mm at 12 months postoperatively. Mean axial length changes was from -0.9mm to -1.74 mm, and there was a statistically significant correlation between decrease in intraocular pressure and axial length shortening [correlation coefficient: 0.545, p<0.05]. Mean corrected visual acuity was 0.69 preoperatively, decreased to 0.27 at 1 week postoperatively [p<0.05], and recovered through 6 months postoperatively. The incidence of decreased corrected visual acuity 2 line or more was 75%, 62.5%, 25%, 25% at 1 week, 1, 3, 6 months respectively. There was a statistically significant correlation between corrected visual acuity change and axial length change [correlation coefficient: 0.568, p<0.05], although no statistically significant correlation between corrected visual acuity changes and corneal astigmatic changes was noted [p>0.05]. Statistically significant decrease in contrast sensitivity occurred upto 1 month postoperatively [p<0.05] and recovered thereafter. In conclusion, we found significantly long-lasting structural and visual function changes following trabeculectomy with mitomycin C, and that structural changes partly affect visual function changes.