Clinical evaluation of the effectiveness of asymmetric intrastromal corneal ring segments with progressive base width for management of keratoconus.

Abstract

Purpose: To evaluate visual, refractive, corneal topographic, and aberrometric results of asymmetric intracorneal ring segments (AS ICRS) with variable width to manage asymmetric keratoconus.

Setting: Quinze-Vingts National Ophthalmology Hospital, Paris, France.

Design: Prospective observational study.

Methods: According to their tomographic pattern, patients receiving one AS ICRS (INTRASEG asymmetric; Gamma Vision) were included. AS INTRASEG features an arc length of 150 degrees and asymmetric width (800 to 1200 µm). Anterior segment optical coherence tomography (AS-OCT) combined with Placido disc MS-39 (CSO, Firenze, Italy) were performed before, 1, and 6 months after surgery to assess keratometric, aberrometric outcomes, and epithelial remodeling. Refractive outcomes were also evaluated. Analysis of the correction profile according to the width of the base of the ICRS was performed.

Results: 43 keratoconic eyes were analyzed. Significant improvement of corrected distance visual acuity was observed (LogMAR): from 0.34 ± 0.23 to 0.08 ± 0.10 (p<0.001). The flattening effect was higher at the widest end than the narrowest end (-10.59D ± 2.59 versus -4.54D ± 1.30, p<0.001), contributing to reduce the Symmetry Index Front from 9.06 ± 4.02 to 2.21 ± 3.81. Total higher orders aberrations reduced from 2.13 ± 0.94 µm to 1.77 ± 0.59 µm (p<0.001) with a halving of the coma aberration from 1.84 ± 0.87 µm to 0.89 ± 0.50 µm (p<0.001).

Conclusion: Implantation of AS INTRASEG in asymmetric keratoconus improves refractive, topographic, and aberrometric parameters. The progressive width of the base is efficient for reducing vertical asymmetry and higher-order aberrations of asymmetric keratoconus phenotype.