The Effect of RGP Lens and Reverse Geometry Lens on Redistribution of Corneal Epithelial Cell in Rabbit

PURPOSE: To investigate the migration and redistribution of rabbit corneal epithelial cells when wearing reverse geometry lens (RGL) or rigid gas permeable lens (RGP). METHODS: In 30 rabbits, the right eyes were fitted with either RGL or RGP and the left eyes were untreated to serve as controls. The rabbits were sacrificed at 1, 3, 7, 10 and 14 days after lens fitting. The central and peripheral corneal thicknesses were measured by microscope and the ratio of right to left corneal thickness was calculated to evaluate the characteristics of change over time. By using the molecular probe 7-nitrobenz-2-ox-1,3-diazolylphallacidin (NBD phallacidin), the samples were examined with light microscope to determine the migration and redistribution of epithelial cells in the rabbit cornea. RESULTS: No consistent changes in the thickness of both central and peripheral corneal epithelium were found. The corneal epithelial cells of both eyes with RGL and RGP reacted positively to NBD phallacidin. The fluorescence was most increased at day 3 of sacrifice in RGL cases and at day 7 in RGP cases, and then decreased in both cases. The corneal epithelium of eyes with RGL exhibited marked increase in the intensity of fluorescence compared to the eyes with RGP. CONCLUSIONS: The corneal epithelium with RGL showed the strongest intensity of NBD phallacidin fluorescence. This result suggests that wearing RGL may induce the migration and redistribution of corneal epithelial cells.

The Influence of Factors Before Wearing Reverse-Geometry Lens on Visual Acuity After Wearing Reverse-Geometry Lens

PURPOSE: To determine whether patient factors (pre-fitting patient's data) before reverse-geometry lens (RGL) use could be predicting factors for the increase in visual acuity after RGL use. METHODS: The authors reviewed out patient records of 805 eyes of 423 patients wearing RGLs from March 2003 to May 2009. The relationship between patient factors on UVA before wearing a RGL examined at follow-ups and the IVA after wearing a RGL were analyzed. RESULTS: The spherical refractive errors and the cylindrical refractive errors showed statistically significant results (p 0.05). CONCLUSIONS: The refractive error and the corneal astigmatism may be strong predictors of UVA and IVA after RGL use.

An Analysis of Correlation with Visual Acuity, Refractive Error and Corneal Astigmatism after Wearing of Reverse Geometry Lenses

PURPOSE: To evaluate correlations with refractive error, astigmatism and uncorrected visual acuity after Ortho-K LKTM lens wear. METHODS: Sixty-one eyes of 32 patients who had been wearing reverse geometry lenses for over 5 weeks were recruited. Uncorrected visual acuity, subjective refraction on retinoscopy, objective refraction measured by an autorefractometer, and corneal astigmatism were measured by corneal topography before, at 2 days, and 1, 3, and 5 weeks after lenses fitting. RESULTS: Uncorrected visual acuity improved from 0.12+/-0.10 to 0.95+/-0.15 after 5 weeks. Subjective refraction on retinoscopy and objective refraction measures with the autorefractometer were -3.52+/-1.65D and -4.06+/-1.73D, respectively before wearing the lenses. These decreased to -0.08+/-0.40D and -1.98+/-2.04D, respectively after 5 weeks. The astigmatism detected by corneal topography improved from 0.93+/-0.49 to 1.20+/-1.03 after 5 weeks. Uncorrected visual acuity was correlated with the refractive error measured by subjective refraction with retinoscopy rather than that by objective refraction with the autorefractometer. Corneal astigmatism measured by corneal topography correlated with the refraction detected by the autorefractometer. CONCLUSIONS: Subjective refraction by retinoscopy rather than refraction found objectively using the autorefractometer, was highly correlated with uncorrected visual acuity (r=0.77~0.87) which seems to be useful in evaluating myopia patients. The astigmatism determined by autorefractometer examination had high correlation with that determined by corneal topography (r=0.51~0.76). This result appears useful in decisions related to the decentering of lenses.

The Effect of RGP Lens and Reverse Geometry Lens on Corneal Epithelial Proliferation Rate in Rabbit

PURPOSE: To investigate proliferation rate of the corneal epithelium with rigid gas permeable lens(RGP) or reverse geometry lens(RGL) wearing. METHODS: Twenty-four rabbits were fitted with either a RGP or RGL on right eye, with left eye serving as a control. They were sacrificed at 1, 3, 7, and 14 days after lens fitting. after immunohistochemistry using 5-bromo-2-deotyuridine, BrdU-labeled cells were counted in 10-medium power fields (X200) in each sample using light microscope by 1.0 mm intervals between superior limbus and the center. RESULTS: The number of BrdU-labeled cells was highest in peripheral cornea, and lowest in limbus(p<0.05). The BrdU-labeled cells of limbus increased by 127% but labeled-cells of the center decreased by 24% in RGP group after 1-day fitting. Increase of the labeled cells was observed in the mid-peripheral and central cornea by 12% and 121% each but the decrease of labelled cells was found at the limbus by 16% in RGL fitting group at 1 day. After 14days, Both RGP and RGL group showed decrease of BrdU-labeled cells in limbus by 8% each, and in the center by 32% and 63%, respectively. CONCLUSIONS: Normal rabbit cornea was characterized by different epithelial proliferation rates according to location. However these pattern was significantly altered with both RGL and RGP fitting group. The change was greater in RGL group than in RGP group. This suggested wearing the RGL might be less physiologic than RGP fitting.

Effect of Reverse Geometry Lens on Correction of Moderate-degree Myopia and Cornea

PURPOSE: To evaluate the effect of reverse geometry lens (RGL) on correction of moderate degree myopia and cornea in patients of moderate-degree myopia. METHODS: 48 eyes of 82 eyes were chosen to wear reverse geometry lens and the remaining 34 eyes were fitted with rigid gas permeable (RGP) lens. The subjects were tested three days, one, two weeks, one, two and three months after fitting the lens. Uncorrected visual acuity, manifested refractive error, corneal thickness and corneal endothelial cell count were evaluated. corneal topography were performed. RESULTS: The uncorrected visual acuity was increased at 0.05 LogMAR after two weeks. and manifested refractive error decreased during the first months, thereafter stabilizing to -0.2 D (diopters). Corneal thickness was 540.4 micrometer and 583.0 micrometer in the center and mid-periphery, decreased to 505.2 micrometer and 572.7 micrometer, respectively, three months after RGL fitting (p<0.05). Endothelial cell count was 2663.5 cells/mm2 and 2541.5 cells/mm2 in the center and mid-periphery, 3 months after RGL fitting and endothelial cell count was not significantly different compared with that of pre-fitting. There was no statistical difference between RGL fitting group and RGP fitting group in the change of corneal endothelial cell count. CONCLUSIONS: RGL was found to be effective in correction of moderate-degree myopia. It had minimal effect on corneal endothelium, in short-term usage, however, the change of corneal thickness suggests that RGL fitting may effect on corneal epithelium and stroma.

The Effect of RGP Lens and Reverse Geometry Lens on Apoptosis in Rabbit Cornea

PURPOSE: To investigate the cytotoxic effect of rigid gas permeable(RGP) and reverse geometry lens(RGL) on rabbit corneal cells. METHODS: In 36 white rabbits, right eyes were worn with either RGP or RGL. Left eyes were served as control. The rabbits were sacrificed at 1, 3, 7, 14 days after fitting and 7, 14 days after removal. Morphological changes of the basal epithelial cells and stromal keratocytes were observed using the light and transmission electron microscopy. The samples were examined after TUNEL staining in 3 high power fields (x400). RESULTS: In control eyes, 2.26% of central corneal epithelial cells showed apoptosis. After RGP wearing, the epithelial apoptosis decreased by 0.32% compared to control eyes(2.17%) at 14 days(p<0.001), and returned to 1.55% at 14 days after lens removal(2.04% in control, p=0.161). After RGL wearing, the degree of apoptosis was also lower than control(3.22%) by 0.30% at 14 days(p=0.003). However, it increased to 0.75% at 14 days after lens removal(1.67% in control, p=0.077). A few TUNEL positive fibroblasts were found in superficial stroma in both RGP and RGL group, but not in control eyes. CONCLUSIONS: Both RGP and RGL wearing may decrease the degree of apoptosis in corneal epithelium and lead the apoptosis in corneal stroma. The degree of apoptosis was recovered after lens removal, suggesting the process might to be reversible. The fitting with RGL induced apoptosis of keratocyte more than the fitting with RGP did. It suggests that the RGL wearing may be less physiologic than RGP wearing.