Optical Evaluation of Intracorneal Ring Segment Surgery in Keratoconus

Area of Science:

• Ophthalmology
• Corneal Surgery
• Optical Engineering

Background:

• Keratoconus is a progressive thinning of the cornea leading to irregular astigmatism and visual impairment.
• Intracorneal ring segments (ICRS) are a surgical option to improve visual acuity and reduce aberrations in keratoconus patients.

Purpose of the Study:

• To evaluate the impact of various intracorneal ring segments (ICRS) combinations on corneal morphology.
• To assess the effect of ICRS on visual performance in patients with keratoconus.
• To compare the outcomes of 5-mm and 6-mm surgical zones for ICRS implantation.

Main Methods:

• Analysis of 124 eyes from 96 keratoconus patients who underwent ICRS surgery.
• Classification into 7 groups based on ICRS disposition and surgical zone diameter (5-mm and 6-mm).
• Pre- and postoperative ophthalmological examinations, including corneal geometry, volume, symmetry, and Zernike polynomial analysis for optical aberrations and Visual Strehl (VS).

Main Results:

• ICRS implantation resulted in significant corneal flattening, particularly on the anterior surface.
• A 6-mm surgical zone diameter showed a more pronounced change in asphericity compared to a 5-mm zone.
• Mean astigmatism was reduced by 2.05 D, with specific combinations showing greater efficacy in reducing astigmatism and coma.
• Best corrected visual acuity improved, and Visual Strehl increased significantly post-surgery.

Conclusions:

• ICRS implantation within a 5-mm zone is more effective for corneal flattening.
• ICRS implantation within a 6-mm zone is effective for reducing astigmatism, especially when smaller asymmetry and flattening are intended.
• Asymmetrical ICRS implants are optimal for regularizing the corneal surface and improving visual outcomes in keratoconus.