Astigmatism and the impact of relaxing incisions after penetrating keratoplasty

Abstract

Purpose: To determine the impact of relaxing incisions for correcting postoperative astigmatism following penetrating keratoplasty.

Methods: Data were collected through the Swedish Corneal Transplant Register. Of the 1161 grafts with complete 2-year follow-up, 131 underwent relaxing incisions. Stepwise multiple regression was used to determine the factors that influenced the extent of astigmatism in diopters (D) (square root transformed). The change in astigmatism brought about by relaxing incisions was evaluated both by subtraction (ie, ignoring angle) and vector analysis.

Results: The overall mean astigmatism was 4.56 D (95% confidence interval [CI]: 4.40-4.73, n = 1161). The final regression model explained only a small proportion of the overall variability of the data (< 5%). There was a slight increase in postoperative astigmatism with recipient age (P = .025), and two of the seven participating clinics achieved lower levels of astigmatism (P = .001 and P = .036, respectively). In patients who underwent relaxing incisions, astigmatism was reduced from 8.40 D (95% CI: 8.0-9.0, n = 131) to 3.80 D (95% CI: 3.5-4.3). The mean difference by subtraction was 4.50 D (95% CI: 4.0-5.0, P < .001, paired t test). Vector analysis showed the overall reduction of astigmatism due to surgery to be 7.90 D (95% CI: 7.2-8.7). Compared with grafts with no refractive surgery, a trend was noted that suggested corrected visual acuity was improved following relaxing incisions.

Conclusions: Relaxing incisions were found to be a safe and effective method for reducing postoperative astigmatism and may improve visual acuity.