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

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.