Posters

120º intracorneal ring segments (ICRS) in keratoconus: refractive, aberrometric and geometric results

Poster Details

First Author: N.Alejandre Alba SPAIN

Co Author(s):    P. Perez-Merino   G. Velarde   I. Jiménez-Alfaro   S. Marcos           

Abstract Details

Purpose:

To describe the effects induce in the cornea by implanting two 120º ICRS in keratocnous patients using optic design tools allowing a customized analysis incluiding geometry (changes by axis incluiding asphericity), corneal aberrations and visual quality metrics (Visual Strehl Ratio) and clinical variables

Setting:

Universitary Hospital

Methods:

A prospective observational study was conducted in 24 patients. A complete ophthalmic evaluation incluiding refraction was performed before and three months after surgery. Also Sheimpflug images were obtained using Pentacam at the same visits. Raw elevation points were extracted from Pentacam and a reconstruction of the central 4 mm of the optic zone of the segments was performed using mathlab, then virtual ray tracing with Zemax was performed. Theis allowed the study of all the meridians with diferent bodies of reference, sphericity, corneal aberrations and Visual Strehl Ratio as well as vector analysis of astigmatism. BCVA was also recorded.

Results:

Reference sphere radius increased (p <0.001). This flattening occurred in the meridian of the incision (p <0.001) while the meridian perpendicular to the segments steepened (p <0.001). There was no significant reduction in high order aberrations but when ICRS were closer  in their inferior end, the comatic aberration decreased (30.49% decrease, p 0.039). Astigmatism decreased (58.14% decrease, <0.001). The axis change was over 60° in 7 patients. Visual Strehl Ratio improved from (p <0.001). There was no statisticall change in BCVA. Spherical equivalent decreased (p 0.012). Refractive astigmatism decreased (71.94 % decrease, p <0.001). SIA was 6.334 ± 2.447 D.

Conclusions:

120º ICRS are very effective in reducing regular astigmatism in patients with keratoconus. Thier effect flattens the axis parallel to them while steepns the perpendicular axis. They can only correct small amounts of coma and for that they need to be placed near each other at the steepest part of the cornea.

Financial Disclosure:

None