Corneal laser procedure for vision improvement in patients with late stage dry age-related macular degeneration - a retrospective observational cohort study

Abstract

Purpose: To determine the safety and efficacy of corneal photovitrification (CPV), a new corneal laser procedure, for vision improvement in patients with late stage dry age-related macular degeneration (AMD). Design: Retrospective observational cohort study Participants: 32 eyes of 17 patients with late stage dry AMD; each eye received a single CPV corneal laser procedure and had 12 months (12m) post-treatment (Tx) follow-up. Methods: Pre- and post-Tx examinations included slit-lamp biomicroscopy, subjective manifest refraction, best corrected distance and near visual acuity (BCDVA and BCNVA), and potential visual acuity (PVA). Additional examinations including contrast sensitivity (CS), corneal topography (CT), ray tracing aberrometry (RTA) and microperimetry (MP) were obtained for a subgroup (n=12) of eyes. Main Outcome Measures: BCDVA, BCNVA, PVA, CS, CT, RTA and MP measurements Results: Safety – There were no complications or adverse events. Efficacy – Mean (± SD) BCDVA improved significantly (p < 0.004) from 20/238 (1.08 logMAR) at baseline to 20/144 (0.86 logMAR) at 12m post-Tx corresponding to 11.0 (± 13.1) letters gained. Mean contrast sensitivity improved significantly (p < 0.05) by a factor of 1.86 from baseline at 12m post-Tx. Conclusions: Subject to the limitation of a small sample size, this pilot study indicates that the CPV corneal laser procedure is safe and efficacious for vision improvement in patients with late stage dry AMD. The CPV Tx mechanism of action involves retinal irradiance distribution modifications that may stimulate patient use of functional, rather than atrophied, retinal regions.

Efficacy Analysis of Corneal Photo-vitrification (CPV) for Improved Vision of Age-related Macular Degeneration (AMD) Eyes

“…The present article will focus on the simplified and/or limiting cases such that analytic formulas are available for key features of CPV. The numerical data of anti-cancer system will be scaled (in time and depth) proportionally to present the trends/features of corneal systems [6,7] without repeating the complex numerical simulations (which will be shown elsewhere).…”

“…We will now analyze our clinical data [6,7] completed using the Clear-K ® Low Vision Aid System (Optimal Acuity Corporation, Austin, TX) based on our mathematical model and the numerical analysis of temperature rise and various effective depths described in Section 3.2: the tissue damage depth (Z D ), temperature penetration depth (Z T ), and conversion depth (Z C ). These depths are governed by the parameters of light intensity and light dose (or irradiation time), and the related threshold values, besides the absorption coefficient (A).…”

“…1 to 9, provide quantitative guidance and/or predictions for the following clinical aspects for our previous clinical studies in animal and human. [6,7] CPV treatment safety and efficacy depend upon:…”

“…Corneal collagen shrinkage has long been used in refractive surgery to change the shape and refractive properties of the cornea [2,3]. Recently, a new corneal procedure, corneal photovitrification (CPV), has produced changes in corneal shape and refractive properties by treating corneal stromal tissue to reduce hydration and increase modulus [6,7]. CPV has been demonstrated to be safe and effective in providing vision improvement to eyes with agerelated macular degeneration (AMD) and other retinal disorders [7].…”

“…Various effective depths including the tissue damage depth, temperature penetration depth and conversion depth, governed by the tissue absorption coefficient, light intensity and dose (or irradiation time), and the related threshold values, are introduced in replacing the conventional penetration depth based on a simple Beer's law. The present modeling system with numerical data will be presented to provide quantitative guidance and/or predictions for the clinical aspects for our previous clinical studies [6,7].…”