Vector analysis of femtosecond laser-assisted astigmatic keratotomy after deep anterior lamellar keratoplasty and penetrating keratoplasty

Abstract

Purpose: To compare the refractive and keratometric changes induced by femtosecond laser astigmatic keratotomy (AK) for suture-out post-keratoplasty astigmatism in deep anterior lamellar keratoplasty (group I) and penetrating keratoplasty (group II).

Setting: Dhahran Eye Specialist Hospital, Dhahran, Saudi Arabia.

Design: Retrospective, comparative, interventional study.

Methods: This study comprised 15 eyes in group I and 35 eyes in group II. All eyes underwent femtosecond AK for suture-out post-keratoplasty astigmatism. The refractive and keratometric measurements were evaluated before and 6 months after AK. The Alpins method for vector analysis was used to evaluate the keratometric changes induced by AK.

Results: The astigmatic correction was 99 and 110% in group I and group II, respectively (p = 0.743) and the success of AK was 43 and 51% in group I and group II (p = 0.966). There was a trend in the magnitude of error toward overcorrection with increased surgically induced astigmatism (r = 0.80 with p < 0.001 in group I and r = 0.70 with p < 0.001 in group II). There was no systemic misalignment in either group. The safety indices were 1.50 (0.19-26.67) and 1.27 (0.12-13.33) in group I and group II, respectively (p = 0.325). The efficacy indices were 1.00 (0.05-24.00) and 0.31 (0.04-2.50) in group I and group II, respectively (p = 0.001).

Conclusions: Femtosecond laser AK has similar safety for correcting suture-out post-DALK and PKP astigmatism; however, it is more effective for DALK. There is a positive correlation between surgically induced astigmatism and magnitude of error.

Keywords: Alpins method; Arcuate keratotomy; Astigmatic keratotomy; Deep anterior lamellar keratoplasty; Femtosecond laser; Penetrating keratoplasty.