The effect of the asphericity of myopic laser ablation profiles on the induction of wavefront aberrations.
OBJECTIVE
To compare the effects of laser profile asphericity on the induction of wavefront aberrations, susceptibility to decentration, and depth of focus in a polymethylmethacrylate (PMMA) model.


METHODS
Four PMMA lenses received an excimer laser ablation of -6 D with a 6-mm optical zone and different amounts of primary spherical aberration (Z(4)(0)): 0, -0.346, -1.038, and -2.076 microm. The curvature of each lens was measured by using surface profilometry, and wavefront changes were computed from curvature differences. Changes in optical quality were compared by treatment simulation of 13 real myopic eyes. The influence of pupil diameter, ablation decentration, and defocus on retinal image quality was measured by using the optical transfer function-based visual Strehl ratio (VSOTF).


RESULTS
Aspheric ablation profiles induced significantly less primary but higher secondary spherical aberration (Z(6)(0)) than did the standard profile; however, Z(4)(0) compensation was incomplete. Simulated treatments with aspheric profiles resulted in significantly better retinal image quality and higher decentration tolerance than did the standard profile. Optical depth of focus was not affected with a 3-mm pupil, whereas with a 6-mm pupil, there was a small but statistically significant decrease in depth of focus.


CONCLUSIONS
Aspheric laser profiles showed theoretical optical benefits over standard ablation profiles for the treatment of myopia, including terms of decentration tolerance. However, there remained profound induction and thus, undercorrection of Z(4)(0), due to loss of laser ablation efficiency in the lens periphery.
Bühren
Jens
J
University of Rochester Eye Institute, Rochester, New York, USA.
Nagy
Lana
L
Yoon
Geunyoung
G
MacRae
Scott
S
Kohnen
Thomas
T
Huxlin
Krystel R
KR
D000328:Adult; D057108:Corneal Wavefront Aberration / Q000209:etiology*; D003867:Depth Perception / Q000502:physiology; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000009:adverse effects*; D008297:Male; D008962:Models, Theoretical; D009216:Myopia / Q000601:surgery*; D019904:Polymethyl Methacrylate; D012160:Retina / Q000502:physiology
D019904:Polymethyl Methacrylate