Evaluation of the difference between intended and measured ablation and its impact on refractive outcomes of the wavefront optimize profile and the S001 Wellington nomogram in myopic spherocylindrical corrections

Abstract

Background: To evaluate the level of agreement between intended and measured ablation of the wavefront optimize profile corrected by the Wellington nomogram in myopic spherocylindrical corrections and assess its impact on refractive outcomes.

Design: Prospective, university-institute setting.

Participants: Eighty-six participants (86 eyes for photorefractive keratectomy group) and 86 participants (86 eyes for laser in situ keratomileusis group) recruited in a consecutive-if -eligible basis.

Methods: Differences between intended and measured ablation were evaluated with Scheimpflug camera. Refractive outcomes were evaluated by means of postoperative spherical equivalent, postoperative defocus equivalent, contrast sensitivity, correction index, difference vector and index of success.

Main outcome measures: Correlation of visual outcomes with intended ablation.

Results: Both groups demonstrated significant over-ablations (16.7±8.5, P<0.001 & 11.8±18.5, P<0.001, respectively). Intended ablation was the primary determinant of the measured difference (r-square 0.769 & 0.765, respectively). Photorefractive keratectomy corrections over 100µ had significant impact on postoperative spherical equivalent, postoperative defocus equivalent, correction index, difference vector and index of success (P=0.044, P=0.05, P=0.019, P=0.016, P=0.006, respectively), but laser in situ keratomileusis corrections over 100µ had significant impact only on postoperative defocus equivalent, difference vector and index of success (P=0.04, P=0.05).

Conclusions: The results suggest that the wavefront optimize profile seems to over-ablate corneal tissue both in photorefractive keratectomy and laser in situ keratomileusis. Over-ablation exerts significant impact on refractive outcomes only in high spherocylindrical corrections.