Comparative Analysis Of Epithelial Thickness Mapping After Manual Versus Femtosecond-Assisted Intrastromal Ring Implantation

To evaluate postoperative epithelial thickness map changes after intrastromal corneal ring segment (ICRS) implantation, comparing manual and femtosecond-assisted techniques in patients with keratoconus.

Tertiary referral ophthalmology center.

This retrospective observational study included keratoconus patients aged ≥18 years who underwent implantation of a 160° intrastromal ring segment between May and October 2024. Epithelial thickness mapping was performed using the Cassia 2 device, with evaluation of central, paracentral, and peripheral corneal zones. Ferrara-type intrastromal corneal ring segments were implanted according to the manufacturer’s nomogram based on Pentacam data. All procedures were performed by the same surgeon. Assessments were conducted preoperatively and at 1 and 3 months postoperatively.

Six eyes underwent femtosecond-assisted ICRS implantation, and six eyes underwent the manual technique, with all procedures performed by the same experienced surgeon.
In the femtosecond-assisted group, mean maximum central epithelial thickness increased from 54 µm preoperatively to 57.67 µm at 3 months postoperatively. In the manual group, mean maximum epithelial thickness increased from 56.33 µm to 57.33 µm over the same period. Although both techniques demonstrated postoperative epithelial thickening, the femtosecond-assisted approach showed a greater increase in epithelial thickness compared to the manual technique.

The femto technique showed a more pronounced initial increase in epithelial thickness, particularly in the central and peripheral areas, reflecting faster epithelial remodeling in the first month post-surgery. However, after three months, the difference between the techniques was minimized, with both showing a significant and sustainable increase in epithelial thickness. Epithelial thickness remained higher than preoperatively in both groups, with the femto technique maintaining slightly better performance in the central and peripheral areas. This suggests that despite the faster initial response of the femto technique, long-term epithelial remodeling is comparable between both approaches.