Topographic Keratometric Effects of Corneal Refractive Therapy After One Month of Lens Wear

Abstract

Abstract: : Purpose: To examine the topographical corneal shape change over a horizontal chord after one month of wearing CRT^TM corneal reshaping contact lenses. Methods: Twenty three participants wore CRT^TM HDS 100 contact lenses in both eyes while sleeping. Topography was measured using the Humphrey Atlas^TM corneal topographer the night prior to lens insertion, immediately after lens removal on the following morning and 1, 3, 7 and 14 hours afterwards at days 1, 4, 10 and 28 and after a 72 hour washout period of no lens wear. Topographic changes were measured over a 6–8mm chord in 1mm steps. Results: There were significant differences in corneal curvature over time (p=0.000), day (p=0.000) and at various corneal locations (p=0.000). The central positions flattened and the mid peripheral positions steepened throughout the month of the study The mean (±sd) change in curvature centrally and at 3mm temporal from the centre was –1.54±1.59D and 2.31±2.26D respectively, immediately after lens removal, at Day 1 and –2.76±1.52D and 4.08±2.41D at Day 28 respectively. On Day 28, after 14 hours, there was little regression noted compared to the morning, 18% centrally and 29% mid–peripherally. At the 72 hour (post–discontinuation) visit, the cornea did not recover to baseline, the central cornea was still flatter (approx. 0.75D, 69% recovery) and the mid–periphery was still steeper by the same amount, representing a 77% recovery. Conclusions: After one month of lens wear, the CRT^TM lens wearing eyes showed a significant topographic shift. The shape of the cornea did not recover to baseline at 14 hours after one month or after a 72 hour recovery period, indicating that the change in shape can be maintained.

Keywords: contact lens • topography • color appearance/constancy