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Cherie B Nau, Michael Helland, Muriel Schornack; Decreased Lens Clearance at 20 Minute Intervals Over 2 Hours of Small-Diameter Scleral Lens Wear. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6070.
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Small-diameter scleral lenses were previously found to settle by about 50% after two hours of wear. The rate of lens settling over time is further evaluated in this study. We examined the clearance between the lens and the cornea at 20 minute intervals during the first two hours of small-diameter scleral lens wear.
Twelve participants, seven men and five women age 21-43 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 15-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 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 Schemipflug 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 152 ± 72 µm (range: 49-315 µm). After two hours of wear, clearance was reduced to 80 ± 55 µm (range: 26-237 µm; p = 0.009), a 47% reduction in corneal clearance. Percent reduction in clearance between successive time intervals was 15%, 2%, 0%, 11%, 8%, and 21% at 20, 40, 60, 80, 100, and 120 minutes after application respectively. Difference in clearance between initial and 20 minutes (128 ± 67 µm, p = 0.005), and initial and 120 minutes were significant. However, the only time interval with a statistically significant change in vault was after the first 20 minutes of wear, difference between other successive intervals were not significant.
There is an initial reduction of central clearance within 20 minutes of 15-mm scleral lens wear. The lens continues to settle after two hours of continuous wear. The potential for lens settling needs to be considered when fitting these lenses.
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