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Cherie B Nau, Michael Helland, Muriel Schornack; Decreased Lens Clearance at 20 Minute Intervals Over 2 Hours of 18.2mm-Diameter Lens Wear. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1478.
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Small-diameter scleral lenses were previously found to settle by almost 50% after two hours of wear. The rate of lens settling over time in larger-diameter lenses is evaluated in this study. We examined the clearance between the lens and cornea at 20 minute intervals during the first two hours of 18.2mm-diameter scleral lens wear.
Thirty-five participants, fourteen men and twenty-one women, age 20-44 years (29 ± 7 years, mean ± SD) with healthy eyes (no history of eye disease or surgery and no previous scleral lens wear), were fitted on one eye with a 18.2-mm diameter Jupiter scleral lens (Visionary Optics, Front Royal, VA). Lenses were selected from a diagnostic fitting set to provide 200-300-μm clearance between the lens and central cornea immediately after application. Within 5 minutes after lens placement, slit images of the lens and cornea were recorded by Scheimpflug photography (Pentacam, Oculus, Inc.). The clearance between the posterior surface of the lens and the anterior surface of the cornea was measured twice, over the central cornea, in each of two vertical Scheimpflug images, using the caliper tool in the Pentacam analysis software. Clearance was recorded as the average of these four measurements. Scheimpflug photography was repeated every 20 minutes for two hours, and the central clearance was measured in the same manner. The corneal clearance for each measurement was compared to the initial clearance and to the previous time point by using a paired t-test.
Scleral lens clearance after initial application was 200 ± 82 µm (range 84-436 µm). After two hours of wear, clearance was reduced to 143 ± 89 µm (range 31 - 394 µm; p < 0.001), a 29% reduction in corneal clearance. Percent reduction in clearance between successive time intervals was 14%, 7%, 5%, 3%, 6%, and -2% at 20, 40, 60, 80, 100, and 120 minutes after application respectively. Difference in clearance between initial and 20 minutes, 20 and 40 minutes, and 80 and 100 minutes were significant.
There is an initial reduction of central clearance within the first 40 minutes of 18.2-mm scleral lens wear. The lens stabilized after 100 minutes of lens wear. The potential for lens settling needs to be considered when fitting these lenses.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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