A novel method for evaluating the thickness and keratometry profiles of toric lenticules created by a new-generation keratorefractive lenticule extraction platform.

PURPOSE: To investigate the thickness and keratometry profiles of toric lenticules created by keratorefractive lenticule extraction (KLEx) using the VISUMAX 800 femtosecond laser platform.

METHODS

This prospective study included the right eyes of 42 patients who underwent KLEx with VISUMAX 800 for correction of myopia and myopic astigmatism. Custom software generated spatial profiles of lenticule thickness (LT) and surgically-induced change in keratometry (SIK) based on raw pre- and postoperative tomographic data. The following indices were calculated: lenticule thickness per unit dioptre (LT/D), LT at the steep and flat meridians and their difference (LTF-S), percentage of lenticule thickness decrease (PLTD) and SIK at the steep and flat meridians.

RESULTS

A significant difference in average LT/D was observed across optical zones (OZ), with LT/D with OZ increasing non-linearly with OZs. The lenticule exhibited a convex shape, thinning more rapidly towards the periphery. Flat LT/D exceeded steep LT/D and the difference (LTF-S) correlated positively with cylindrical error. Flat PLTD was lower than steep PLTD, indicating a slower rate of thickness decrease along the flat axis. Steep SIK exceeded flat SIK within the central 1-2 mm but was lower than flat SIK from 4 to 7 mm.

CONCLUSIONS

The spatial profiles of LT and SIK reflect the toric treatment module for astigmatic correction. This study introduces a method for in vivo measurement of lenticular spatial profiles, enabling quantitative assessment of lenticule geometry.