Novel Objective Method for Comparing Ablation Centration With and Without Pupil Tracking Following Myopic Laser In Situ Keratomileusis Using the Bausch & Lomb Technolas 217A

Abstract

To apply an objective method to topographically determine functional optical zone (TFOZ) dimensions in order to compare ablation centration, and refractive outcomes, following myopic laser in situ keratomileusis (LASIK) with and without automated, infrared (IR) pupil tracking. Thirty-seven eyes that underwent LASIK using the Technolas 217A with active IR pupil tracking (IT) were retrospectively compared to 37 matched eyes treated with manual tracking (MT). Visual acuity, refractive error, and corneal topography were measured pre- and postoperatively. Videokeratography and specialized software were used to assess centration. The IR-tracked eyes had statistically better mean postoperative spherical equivalent (IT +0.02 +/- 0.38 D; MT -0.21 +/- 0.48 D; P = 0.03) and uncorrected distance visual acuity (IT +0.07 +/- 0.08 logMAR; MT +0.02 +/- 0.09 logMAR; P = 0.02). One versus three eyes lost 1 line of best spectacle-corrected visual acuity in the IT and MT groups, respectively. While similar mean displacement of the TFOZ center from the pupil center was found in the MT (0.54 +/- 0.27 mm) and IT (0.51 +/- 0.21 mm) groups (P = 0.77), 4 MT eyes (10.8%) were topographically decentered >1.0 mm, whereas the ablation center was within 1 mm of the pupil center for all IT eyes. Custom software provided a novel, objective method to determine topographic functional optical zone dimensions, then mathematically calculate the center of the optical zone relative to the pupil center and measure the vector of decentration. Use of IR pupil tracking improved uncorrected visual acuity, produced more predictive refractive outcomes, and fewer large centration outliers. This may reflect increased fidelity of spot placement to the attempted ablation profile.