PURPOSETo investigate changes in epithelial thickness after overnight wear of CRTH rigid gas-permeable (RGP) lenses (Paragon Vision Sciences, Mesa, AZ) for the correction of hyperopia.METHODSTwenty subjects wore a +3.50 D hyperopia-correcting CRTH lens on one eye for a single night in an attempt to induce myopia (first study). The untreated eye served as the control. Corneal and epithelial thickness was measured at nine points across the horizontal meridian by OCT. Measurements were obtained the night before lens wear, immediately after lens removal the next morning, and 1, 3, 6, and 12 hours after removal. Measurements were obtained 28 hours later, to observe recovery. Then, the attempted hyperopic corrections of +1.50 and +3.50 D were evaluated, using CRTH lenses in both eyes of 20 subjects for a single night (second study).RESULTSAll values were compared to baseline unless otherwise stated. In the first study, the treated eye's central and midperipheral epithelial thickness increased by 21.5% +/- 8.6% and 13.3% +/- 7.6%, respectively, after lens removal (P < 0.001). The control eye's central epithelial thickness (CET) increased by 7.1% +/- 6.0% (P < 0.05). In the second study, CET increased by 17.6% +/- 8.5% (P < 0.001) in the +3.50 D-treated eye and by 13.3% +/- 4.8% (P < 0.001) in the +1.50 D-treated eye. Midperipheral epithelial thickening was 5.9% +/- 4.7% (P < 0.05) in the +3.50 D-treated eye and 6.0% +/- 6.3% (P < 0.05) in the +1.50 D-treated eye.CONCLUSIONSCRTH lenses, designed to correct hyperopia, when worn overnight, caused an increase in CET. The amount of epithelial change seemed to differ with modified lens design.

Purpose. To measure corneal and epithelial thickness across four meridians using Optical Coherence Tomography (OCT) and to compare these measurements between normal non-lens wearers (NLW), rigid gas permeable (RGP) lens wearers, and RCP-wearing keratoconics (KC).Methods. Both eyes of 60 Subjects were measured (20 NLW, nine female:11 male, 27.6 +/- 5.9 years; 20 RGP, 20 female, 23.9 +/- 7.6 years; and 20 KC, seven female:13 male, 32.4 +/- 8.1 years). A customized fixation target employing LEDs in eight directions of gaze was attached to the OCT and corneal images obtained. Raw OCT scans were analyzed to yield values for cornea) and epithelial thickness and color-coded maps were compiled.Results. Central corneal thickness (CCT) was thinnest in KC (447 +/- 68 mu m) and similar between RGP (518 +/- 32 mu m; P-KC < 0.001) and NLW (517 +/- 21 mu m) (P-KC < 0.001 NLW > 0.05). Peripheral corneal thickness in NLW was thickest in the superior temporal and thinnest in the interior (1) regions (superior temporal(thickest) vs. l(thinnest) p < 0.001). Central epithelial thickness was thinnest in KC (44 +/- 7 mu m), followed by RGP (50 +/- 4 mu m), then NLW (54 +/- 2 mu m) (P-KC < 0.001 NLW p(RGP) < 0.05). Central epithelial thickness in the KC group was significantly thinner than in the RGP group (p < 0.001). In the NLW group, peripheral epithelial thickness was thicker (63 +/- 5 mu m) than central (p < 0.001) and was thickest in the superior (S) region and thinnest in the interior (1) region (S-thickest vs. I-thinnest p < 0.001). KC epithelium was thinnest in the interior temporal meridian (42 +/- 5 mu m).Conclusions. Thickness of the normal cornea and epithelium was greatest in (lie Superior region. In all groups, the inferior cornea and epithelium was thinnest, and to a greater extent in the KC group. (Optom Vis Sci 2008;85:963-976)

Purpose. To assess the corneal swelling response to two myopic correction corneal refractive therapy (CRT) lenses of varying Dk/t values, worn for a single night. Change in thickness of the total cornea, stroma, and epithelium was measured across the horizontal meridian using optical coherence tomography (OCT). Methods. In this double-masked, randomized study, twenty subjects wore a CRT design lens in each eye, manufactured from Menicon Z (MenZ; Dk/t = 91) and Equalens II (EqII; Dk/t = 47) materials. Baseline corneal thickness was measured centrally and at four points either side of the central cornea using OCT, the night before sleeping at the Centre for Contact Lens Research. The next morning, lenses were removed, and thickness measurements were repeated 1, 3, 6, and 12 h after removal. Results. On lens removal, the MenZ eye had central and paracentral corneal swelling (mean ± SD) of 4.1 ± 2.0% and 5.6 ± 2.4%, and the EqII eye had 5.8 ± 2.6% and 7.0 ± 2.6%. These values were significantly different from baseline (ReANOVA; p < 0.001) and were different between lens materials (p < 0.001). The central epithelium thinned by 10.0 ± 4.5% in the MenZ eye and by 10.2 ± 8.5% in the EqII eye, with the mid-peripheral epithelium thickening by 13.4 ± 7.9% in the MenZ eye and 18.3 ± 9.8% in the EqII eye (all changes different from baseline p < 0.001). These epithelial values were not statistically different between materials (p > 0.05). Stromal swelling values on lens removal were 5.7 ± 2.2% centrally and 5.5 ± 3.0% mid-peripherally (MenZ) and 7.7 ± 3.1% centrally and 6.6 ± 2.9% mid-peripherally (EqII) (all p < 0.001 from baseline). Central stromal swelling was different between eyes at lens removal (p < 0.001). Stromal thickness in both eyes returned to baseline values within 3 h. Conclusion. The higher-Dk/t MenZ material caused significantly less overnight corneal and stromal swelling than the Eqll material, which reinforces the need to prescribe lenses with high Dk/t for overnight wear. Neither central epithelial thinning nor paracentral thickening are significantly affected by Dk/t.

PURPOSE:To investigate thickness changes of the total cornea and epithelium across the horizontal corneal meridian after 4 weeks of overnight corneal refractive therapy (CRT) rigid contact lens (Paragon Vision Sciences, Mesa, AZ) wear.METHODS:Thirty subjects were fitted with CRT contact lenses (Dk/t = 67), which were worn overnight for 4 weeks. Corneal thickness was measured at nine locations along the horizontal meridian by using optical coherence tomography (OCT) before lens insertion in the evening. Corneal thickness was measured the next morning immediately after lens removal and 1, 3, 7, and 14 hours later. This was repeated on days 4, 10, and 28 of the study and then 3 days after discontinuing lens wear.RESULTS:Twenty-three subjects completed the study. At lens removal on day 1, the central and paracentral cornea swelled by 4.9% and 6.2%, respectively (both P = 0.000). The central epithelium thinned by 7.3%, and the mid peripheral epithelium thickened by 13% (both P = 0.000). Corneal swelling recovered throughout the day, with most of the deswelling taking place within the first 3 hours after lens removal. Maximal central epithelial thinning reached 13.5% by day 4. Three days after the study completion, corneal and epithelial thickness had recovered to baseline values.CONCLUSIONS:This study shows that CRT lenses induce differential overnight swelling across the cornea, with rapid deswelling during the day. Central epithelial thinning and paracentral thickening occurs, with recovery 3 days after discontinuation of lens wear.