First-in-human laser-induced refractive index change (LIRIC) treatment of the cornea

Abstract

Purpose : Corneal laser induced refractive index change (LIRIC) has been previously demonstrated in cat and rabbit animal models and ex-vivo human cornea (previously known as IRIS). The present study is the first to assess the safety of performing LIRIC - a patterned, fs-laser induced refractive index modification of the cornea - in human patients.

Methods : Five partially-sighted pseudophakic eyes of 5 patients (3 female; age: 68±15yrs) were instilled with topical anesthetic (proparacaine, 0.5%), immobilized with a suction ring and flat applanated with a custom-built patient interface. All treated eyes had pre-existing low vision conditions such as macular holes. The LIRIC procedure did not require dopants, epithelial removal or flap cutting. Each eye was treated with an 82s duration exposure of a 405nm wavelength fs-laser focused in the central cornea (250µm depth). A custom-built system scanned the laser focal point across a 3mm diameter optical zone while simultaneously modulating laser power to impart a +2.5D diffractive bifocal wavefront. At the time of abstract submission, eye exams were performed pre-operatively, 1 day, and 1 week post-operatively, with remaining visits of 1, 3, 6 and 12 months to be conducted. To assess safety, eye exams included slit lamp imaging, anterior segment optical coherence tomography (OCT; Copernicus+, Optopol), pachymetry and topography (Galilei, Ziemer).

Results : All 5 patients were successfully treated with LIRIC. At all post-operative time points the cornea appeared clear under slit lamp examination. There was no evidence of corneal or conjunctival inflammation, scarring, or opacity. The LIRIC pattern was visible with slit lamp and OCT. Notably, there were no significant changes (paired Student’s t-test, p>0.60) in anterior corneal curvature (mean change: 0.08±0.38D), posterior corneal curvature (0.02±0.11D), or corneal central thickness (-3.8±15.9µm) between the pre-operative and 1 week post-operative time points.

Conclusions : The first-in-human study of LIRIC indicated a good, early safety profile with clear corneas, no evidence of inflammation, scarring, or opacity. Further studies are needed to assess visual efficacy and establish long-term stability. However, this study is an essential first step in establishing laser-induced refractive index change as a new, ablation-free, tissue-sparing method to correct ocular refractive errors without causing a change in corneal shape.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.