Corneal asphericity after refractive surgery

Abstract

In their recent article on corneal asphericity after surgery, Bottos et al.1 present changes in Q (corneal asphericity) for myopic and hyperopic corrections, indicating that Q values tend to become more positive after myopic ablation and more negative after hyperopic ablation. Such trends have been shown and explained.2–4 The previous articles also provide equations that explain the tendencies in postsurgical corneal asphericity shown by Bottos et al. and the fact that the greater the initial degree of ametropia, the greater the asphericity changes. Bottos et al. claim their results are original, as they were the first to measure corneal asphericity and spherical aberration from Scheimpflug imaging. However, this is to be expected as the fact of measuring corneal asphericity with another instrument cannot change the trends in corneal asphericity after laser in situ keratomileusis. Small changes would be expected with different instruments but not different trends. In fact, the trend in the results of Bottos et al. coincide with those demonstrated by Anera et al.2 and Jiménez et al.3,4 What is missing is an analysis that explains the results and causes of the corneal asphericity changes based on the various articles on this subject.4,5 Furthermore, a more exhaustive analysis of the results could provide information about the type of algorithm used, this being a crucial issue in this type of work. The algorithm is the main cause of corneal asphericity changes, although other variables such as corneal biomechanics and physical aspects of the ablation also have significant influence on the postsurgical corneal shape.