Posters

Contact lens-assisted corneal cross-linking (CXL) for pellucid marginal degeneration

Poster Details

First Author: A. Stuart UNITED KINGDOM

Co Author(s):    R. Angunawela   D. Gore                 

Abstract Details

Purpose:

PMD is characterised by ectasia 1 - 3 mm from the limbus in the 4 – 8 o’clock position. Standard 9 mm diameter CXL ultraviolet (UV) light sources do not adequately cover this area. Decentering the UV spot inferiorly beyond the limbus to improve coverage risks localised stem cell damage. In this study we investigated UV light transmission through silicone hydrogel contact lenses designed to block UV light as part of a modeled CL-assisted limbal shield for use when decentering the treatment spot.

Setting:

Moorfields Eye Hospital, London, UK

Methods:

Three lens models (Acuvue Oasys, Acuvue Moist and Acuvue Advance) were irradiated (n=5, wavelength 375nm, irradiance 10mW/cm2), with the lens placed directly over the UV light meter. The same lenses were then re-tested (n=5) following a 10-minute soak in 0.1% riboflavin. Serial control measurements were taken with no contact lens covering the UV light meter. For limbal-shielding, we modeled an eccentrically punched (11.5mm) standard-diameter lens placed with the widest rim over the inferior limbus. The free cap was moved superiorly exposing an off-axis crescent of inferior cornea for irradiation. Corneal exposure was analysed using Java-based imaging software (ImageJ, 1.48v).

Results:

We recorded mean (SD) control UV irradiance of 10.41 (0.40) mW/cm². Through-lens irradiances were: Oasys, 0.44 (0.14) mW/cm²; Advance, 1.11 (0.15) mW/cm²; Moist, 2.93 (0.16) mW/cm², representing a reduction in UV transmission of 96%, 89% and 72% respectively. Following riboflavin soak, irradiances were: Oasys, 0.30 (0.09) mW/cm²; Advance, 0.58 (0.18) mW/cm²; Moist, 0.81 (0.18) mW/cm², representing a reduction in UV transmission of 97%, 94% and 92% respectively. The addition of riboflavin significantly attenuated UV transmission through Moist and Advance lenses (p<0.01); no significant difference was observed through Oasys lenses (p=0.1). Lens-shielding increased inferior corneal exposure by 27%, covering the 4–8 o’clock position without limbal exposure.

Conclusions:

Not all UV-blocking contact lenses offer the same level of UV attenuation. The Acuvue Oasys lens (without pre-soaking with riboflavin) would appear a good candidate for limbal stem cell protection when decentering the UV light source. This may be applicable for PMD or other peripheral progressive thinning disorders (e.g. melts).

Financial Disclosure:

NONE