Relationship Between Corneal Shape and Refractive Power Pre- and Post- Custom LASIK

Abstract

Abstract: : Purpose: To determine the relationship between corneal shape and refractive power changes following Custom LASIK (using the LADARVision^TM laser coupled with the CustomCornea^TM Measurement Device). Methods: 100 eyes of 50 consecutive bilateral myopic Custom LASIK patients were included in the study. Orbscan II^TM topography and manifest refraction were performed preoperatively and at 6 month post-operatively. The change in manifest refraction (corrected to the corneal plane) (CMSE) before and after Custom LASIK and the corneal shape change as determined from the radii of curvature change averaged within the 2.0, 4.0, and 6.0mm corneal diameter zones (keratometric tangential map) were used for analysis. Results: The average change in CMSE centrally was 2.89D. ± 1.25. At the 2mm, 4mm and 6mm zones the average change in corneal radius was –2.48D ± 1.33, -1.91D ± 0.94 and –1.01D ± 0.74, respectively. The central 2.0 and 4.0 mm diameter zones resulted in the highest and statistically significant correlations between CMSE and measured corneal shape changes (r= -0.74, -0.71 for the 2.0, 4.0mm zones respectively, P<0.05). There was a weak but significant correlation between the 6.0mm diameter zone and CMSE (r= -0.38, P<0.05). Conclusions: A high correlation was found between the central corneal shape and refractive power changes following Custom LASIK but the correlation decreases progressively towards the paracentral zone. This study was support by Alcon.

Keywords: refractive surgery: corneal topography • imaging/image analysis: clinical • topography