Journal of cataract and refractive surgery | 2019
Noninvasive real-time assessment of riboflavin consumption in standard and accelerated corneal crosslinking.
Abstract
PURPOSE\nTo estimate the noninvasive riboflavin concentration in the corneal stroma using a new ultraviolet-A (UVA) theranostic device for corneal crosslinking (CXL).\n\n\nSETTING\nVision Engineering Italy srl, Rome, Italy.\n\n\nDESIGN\nExperimental study.\n\n\nMETHODS\nFourteen human donor corneas were treated according to conventional (UVA irradiance of 3\xa0mW/cm2 for 30\xa0minutes) and rapid (10\xa0mW/cm2 for 9\xa0minutes) riboflavin-UVA CXL protocols using a theranostic UVA device. Five additional samples were treated by 0.5\xa0mW/cm2 for 9\xa0minutes and used as positive controls to determine riboflavin photodegradation under near ambient lighting conditions. A 20% dextran-enriched 0.1% riboflavin solution was used in all cases. The device consisted of a UVA light source; a red-green-blue camera, which acquires the fluorescence images of the cornea during treatment; and a single-board computer for managing the overall operations and the raw data processing.\n\n\nRESULTS\nPreirradiation stromal soaking for 30\xa0minutes achieved highly consistent intrastromal riboflavin concentration in all tissues (mean 0.015%\xa0±\xa00.003% [SD]). There were no differences in the\xa0kinetics curves of riboflavin consumption between the 2 UVA irradiation protocols; the intrastromal riboflavin concentration decreased exponentially, with a mean constant energy rate of 2.8\xa0±\xa00.2\xa0J/cm2. In the control group, the intrastromal riboflavin concentration decreased quasilinearly.\n\n\nCONCLUSIONS\nThe theranostic device provided estimates of the intrastromal concentration of riboflavin noninvasively during treatment. In the 3 to 10\xa0mW/cm2 range of power densities, the consumption of riboflavin in the stroma by UVA irradiation was only energy dependent in accordance with the Bunsen-Roscoe law.