Abstract
Purpose:
To compare the objective Point Spread Function (PSF) calculated for aberrations centered on the corneal vertex (PSFcv) and the objective PSF calculated for aberrations centered on the entrance pupil center (PSFpc) with the subjective PSF drawn by the subject (PSFsubj).
Methods:
Retrospective case series from consecutive patients treated with hyperopic LASIK using the MEL80 at the London Vision Clinic. All standard non-wavefront-guided ablations were centered on the corneal vertex (CV). Eyes were split into two groups depending on the pupil offset value: small angle kappa for eyes with pupil offset ≤0.25 mm (n=15), large angle kappa for eyes with pupil offset ≥0.55 mm (n=20). Atlas corneal topography and WASCA whole eye aberrometry were measured at the 1-year post-operative visit. PSFcv was generated from corneal higher order aberrations using the Atlas 9000 review software. PSFpc was generated from whole eye higher order aberrations using the WASCA. PSFsubj was drawn by the subject while looking monocularly at a bright spot light. Correlation between PSFs was qualitatively evaluated in terms of orientation and size.
Results:
The dominant aberration seen on both the objective PSFs (PSFcv and PSFpc) and the subjective PSF was coma-like aberration. In the large angle kappa group, PSFcv and PSFpc were correlated in 10 out of 20 eyes; and in 9 out of these 10 eyes PSFsubj was also correlated to the objective PSFs. Of the 10 remaining eyes, PSFsubj correlated well with PSFcv in 8 eyes, and with PSFpc in 1 eye, and did not correlate with either PSFcv or PSFpc in 1 eye. In the small angle kappa group, PSFcv and PSFpc were correlated in 7 out of 15 eyes; in 4 out of these 7 eyes PSFsubj was also correlated to the objective PSFs while in the 3 other eyes, the subjects reported no subjective coma. In the 8 remaining eyes, PSFsubj correlated well with PSFcv in 6 eyes, and did not correlate with either PSFcv or PSFpc in 2 eyes.
Conclusions:
Refractive surgery procedures are relatively insensitive to decentrations as demonstrated by the fact that PSFcv and PSFpc were similar in around half of the cases. However, in the majority of cases where there was a discrepancy, PSFsubj correlated better with PSFcv. This would indicate that, from a subjective vision point of view, corneal vertex centration is a slightly better option.
Keywords: 684 refractive surgery: optical quality •
626 aberrations