Analysis of excimer laser treatment outcomes and corresponding angle κ in hyperopic astigmatism

Abstract

To investigate the prevalence of preoperative, intraoperative, and postoperative angle κ in hyperopic eyes and its effect on the refractive outcomes of excimer laser vision correction. University Hospital Hamburg and Care Vision Refractive Centers, Germany. Retrospective multicenter study. Hyperopic patients after laser insitu keratomileusis and before retreatment because of hyperopic regression were included. Three treatment groups were defined based on the magnitude of preoperative angle κ defined as low (<0.25mm), moderate (0.25 to 0.50mm), or high (>0.50mm). The study analyzed 170 hyperopic eyes of 112 patients (mean age 29.8years±10.04 [SD], range 21 to 62years). The preoperative angle κ was low, moderate, or high in 23, 49, and 98 cases, respectively. In eyes with a preoperative angle κ of 0.25mm or more, changes in the x-axes and y-axes of angle κ and its magnitude were statistically significant (P<.05) between preoperative and intraoperative measurements. In these eyes, intraoperative angle κ (offset) was statistically significantly smaller (P<.05), and Purkinje images were statistically significantly more caudal (P< .001). Treatment predictability was independent from using preoperative or intraoperative angle κ, and there were no statistically significant differences in efficacy or safety. A preoperative magnitude of angle κ as high as 0.50mm or higher was present in more than 50% of regressed hyperopic eyes. Measuring angle κ preoperatively did not reflect its real-time intraoperative magnitude. Using the preoperatively larger angle κ as an intraoperative offset might result in a too nasally centered ablation that causes topographic and optical drawbacks; therefore, centering the ablation based on the intraoperative measured offset is recommended.