Abstract
Purpose: :
To determine the relationship between corneal topographical power changes and achieved refractive correction induced by myopic laser in situ keratomileusis (LASIK), and to compare this relationship between custom and conventional ablation platforms.
Methods: :
Medical records of 341 refractive myopic ablations performed between January 2005 to January 2007 were reviewed: 108 had customized ablations and 233 had conventional ablations. Inclusion criteria were uncomplicated LASIK for myopia or myopic astigmatism, follow-up for at least 3 months post-op with stable post-operative refraction and corneal topographic measurements, best-corrected visual acuity (BCVA) of 20/20 or better, and the absence of topographic irregularities such as paracentral ablation patterns or central islands. Linear and non-linear regression analyses were performed to determine the relationship between achieved refractive correction and corneal power changes as measured by corneal topography. Comparisons were then made to evaluate for differences in this relationship between custom and conventional platforms.
Results: :
Corneal topographic power changes and myopic refractive correction are related in a non-linear fashion for refractive changes under four diopters for both custom and conventional platforms. It approaches a linear relationship for corrections above 4 diopters in both platforms. For every unit of refractive correction achieved, custom ablations yielded a statistically significant greater change in corneal topographic power than conventional ablations.
Conclusions: :
Customized myopic ablations yield a larger change in corneal topographical power than conventional ablations. The relationship between corneal power changes and refractive correction is a non-linear relationship in corrections less than or equal to four diopters.
Keywords: refractive surgery: LASIK • refractive surgery: comparative studies • refractive surgery: corneal topography