Abstract
Purpose: :
The concept of internal aberrations (ocular - anterior corneal surface wavefront errors calculated in the same optical plane) is integral to the use of wavefront guided refractive surgery. If internal aberrations include the contribution of the crystalline lens and posterior surface of the cornea, as is the current hypothesis, then for most successful refractive surgery it would be expected that the internal aberrations undergo no significant change following refractive surgery. The purpose of this project was to compare the pre and post operative internal aberrations following excimer laser (AMO S4) wavefront guided (AMO, Wavescan) refractive surgery for myopia and astigmatism.
Methods: :
Retrospective analysis of 250 eyes randomly selected from >2000 eyes having undergone advanced surface ablation (ASA) at the University of Ottawa Eye Institute. Ocular wavefront aberrations were obtained using a Shack-Hartmann wavefront sensor (AMO, Wavescan) pre-op and 3 months post-op. Anterior corneal surface wavefront aberrations were calculate from corneal topography (Pentacam or Orbscan) obtained at the same time points as ocular wavefronts using custom software.
Results: :
Internal aberrations change significantly following ASA surgery. Following refractive surgery internal cylinder iC...Similarly the internal component of the ocular spherical aberration, iSA, increases following surgery.
Conclusions: :
Internal aberrations calculated using ocular wavefront and cornea topography data show significant changes following refractive surgery. Changes in internal aberrations suggest that either there are significant changes in topography of the posterior corneal surface following surgery or that current methodologies for calculating internal aberrations need to be refined. This could have a significant impact on our approach to optimize aberration corrections, especially astigmatism.
Keywords: refractive surgery • aberrations • refractive surgery: optical quality