Noninvasive real-time assessment of riboflavin consumption in standard and accelerated corneal crosslinking.

PURPOSE

To estimate the noninvasive riboflavin concentration in the corneal stroma using a new ultraviolet-A (UVA) theranostic device for corneal crosslinking (CXL).

SETTING

Vision Engineering Italy srl, Rome, Italy.

DESIGN

Experimental study.

METHODS

Fourteen human donor corneas were treated according to conventional (UVA irradiance of 3 mW/cm for 30 minutes) and rapid (10 mW/cm for 9 minutes) riboflavin-UVA CXL protocols using a theranostic UVA device. Five additional samples were treated by 0.5 mW/cm for 9 minutes 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.

RESULTS

Preirradiation stromal soaking for 30 minutes achieved highly consistent intrastromal riboflavin concentration in all tissues (mean 0.015% ± 0.003% [SD]). There were no differences in the kinetics 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 ± 0.2 J/cm. In the control group, the intrastromal riboflavin concentration decreased quasilinearly.

CONCLUSIONS

The theranostic device provided estimates of the intrastromal concentration of riboflavin noninvasively during treatment. In the 3 to 10 mW/cm 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.