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CORNEAL BIOMECHANICAL CHANGES AND HIGH ORDER ABERRATIONS VARIATIONS FOLLOWING THE SHORT TERM WEAR OF A CUSTOMIZED ORTHOKERATOLOGY LENSES
Langis Michaud, Patrick Simard, Rémy Marcotte-Collard;
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the short term impact of a customized OK lens wear on biomechanical properties of the cornea and HOAs
All patients newly fitted in OK lenses at Universite de Montreal (June-Sept. 2019) were recruited. In addition to regular baseline testing, corneal hysteresis (ORA, Reichert, US) and aberrometry (iTrace, Clarion, US) were conducted, before fitting, then repeated at 1 week and 1 month after delivery of the lenses. The additional testing were performed before cycloplegia and always at the same time of the day (+ 1h00). OK lenses were designed through RGP Designer software and customized to the ocular parameter of each participant. Both eyes were tested but only one, randomly selected, was kept for analysis (ANOVA –repeated measures).
64 participants were recruited (37 M, 27 F; 53% Caucasian , 47% Asian, Average age 11.7 + 0.7 years old, -5.75 + 1.97D, AL 24.63 +1.15mm ) and completed the study. Based on topography analysis taken after 1 week, customized OK lenses generated an add power of +9.6 + 0.45 D on the nasal quadrant, +9.2 + 3.9 D temporally, 9.2 + 3.1 superiorly and 9.4 + 2.1 inferiorly. Corneal hysteresis (CH) varied from 11.5 + 2.1 mm Hg to 11.3 + 2.0 mm Hg (1 week) and 11.4 + 0.7 mm Hg after 1 month. These modifications were not found statistically significant (p>0.05- ANOVA repeated measures). Total high order aberrations (HOA) were evaluated at 0.167 + 0.0739 mm at baseline, significantly increasing up to 0.499 + 0.239 um (1 week = +199%) and 0.576 + 0.296 (1 month = +244%; - p<0.05). Comas are mostly responsible for this varation (0.165 to 0.522 and 0.566 um) followed by positive spherical aberration (0.06 to 0.285 and 0.251). Each of these variations were found statistically significant as well. However, participants did not report perception of disturbing haloes and glare during the day.
Short term customized OK lens wear, with very high add power (+9D) has no impact on the corneal hysteresis, but is associated with a significant variation of the overall HOA, more specifically of coma and positive spherical aberrations, the latter being a known factor acting against myopia evolution. Customization of the design helps to increase the level of positive aberrations and then may contribute to a better myopia control.
This is a 2020 ARVO Annual Meeting abstract.
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