Relaxing incision guided by videokeratography for astigmatism after keratoplasty for keratoconus

To evaluate the efficacy of topographic measurements for relaxing incisions in astigmatism following penetrating keratoplasty for keratoconus.

Twenty patients (20 eyes) had relaxing incisions between July 1989 and August 1994 for high astigmatism after penetrating keratoplasty for keratoconus. Ten eyes were evaluated using a HaagStreit keratometer (1989-1991) and 10 eyes were evaluated using EyeSys videokeratography (1991-1994). Relaxing incisions were performed at the steep meridians in the donor/host wound.

Mean preoperative astigmatism was 7.75 +/- 2.05 D (range, 4.50 to 12.00 D) for the keratometry group, and 6.49 +/- 3.24 D (range, 1.11 to 10.13 D) for the videokeratography group. Mean astigmatism following relaxing incision was 3.90 +/- 2.02 D (range, 0.93 to 6.50 D) for the keratometry group and 3.06 +/- 1.62 D (range, 0.07 to 5.64 D) for the videokeratography group (no significant difference). Vector analysis revealed a vectorial change of 4.64 +/- 2.54 D for the keratometry group and 4.68 +/- 2.08 D for the videokeratography group (no significant difference). Mean spectacle-corrected visual acuity was significantly improved in the topography-guided group following the procedure (P = .021). Complications included perforations in 3 of 20 eyes. Four patients (4 eyes) in the keratometry group and one patient (1 eye) in the videokeratography group had residual astigmatism greater than 5.00 D. Four patients in the keratometry group needed a second procedure of relaxing incision because of irregular (2 eyes) or high (2 eyes) astigmatism. One patient (1 eye) in the videokeratography group needed a second relaxing incision.

Videokeratography as a guide for relaxing incision has some benefits over standard keratometry. Preoperative evaluation with videokeratography did not significantly improve the postoperative astigmatism. Fewer reoperations were needed when videokeratography was used.