Effects of Ocular Parameters on Diameter of Well-fitted Rigid Gas Permeable Lens in Koreans

PURPOSE: To compare the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting. METHODS: Ninety-three eyes of 49 patients were prescribed RGP contact lenses (YK spherical lens, Lucid Korea, Bonghwa, Korea) by a single ophthalmologist at the same hospital. We analyzed the differences of parameters of 9.3 mm and 8.8 mm rigid gas permeable lenses (RGP lenses) that were prescribed by trial lens fitting. Steep keratometric value (Ks), flat keratometric value (Kf), and corneal astigmatism (Kast) were measured by keratometer. Simulated steep keratometric value (Sim Ks), simulated flat keratometric value (Sim Kf), simulated corneal astigmatism (Sim Kast), white to white corneal diameter (WTW), and eccentricity were measured by corneal topography. We also analyzed the differences of back optic zone radius (BOZR) and lens power between the two groups. RESULTS: In this study, 40 eyes wearing 8.8 mm lenses and 53 eyes wearing 9.3 mm lenses were included. Keratometric value and eccentricity were significantly higher in the 8.8 mm lens group, while WTW and BOZR were significantly lower. Corneal astigmatism (Kast, Sim Kast) and lens power were not significantly different between the groups. CONCLUSIONS: RGP lenses with a smaller diameter were likely to be prescribed to patients with higher keratometric value, higher eccentricity, and shorter WTW, and the average BOZR of the prescribed RGP lenses with a smaller diameter was likely to be steeper.

Effect of the Aspheric RGP Lens on Corneal Topography and Endothelial Cell in Keratoconus

PURPOSE: To analyze the effects of the aspheric rigid gas permeable (RGP) lens on the corneal topography and endothelial cells in eyes with keratoconus. METHODS: Sixty five eyes of 35 keratoconic patients who had follow-up of more than 6 months were included in the study. Thirty eyes of 16 patients wore aspheric RGP lens, and the remaining control eyes did not wear any lens. After aspheric RGP lens fitting, visual acuity and manifest refractive error were evaluated, Slit lamp examination and corneal topography were also done. Mean cell area and density of corneal endothelial cell were measured by specular microscopy at first visit and 6 months after lens fitting. RESULTS: After lens fitting, the percentage of best corrected visual acuity of better than 20/25 was 93.3% (28 eyes). The change of astigmatism, the Steepest Simulated keratometry reading, Surface asymmetry index, Surface regularity index, and apical corneal power were significantly increased in the keratoconic cornea in aspheric lens fitting group compared to the control group (p0.05). CONCLUSIONS: Short-term wearing of aspheric RGP lens in keratoconic patients showed no effect on corneal endothelial cells. However, it increased the irregularity and steepening of the keratoconic cornea. It may indicate that mid-peripheral corneal-to-lens relationship may be inappropriate when keratoconus is fitted with aspheric lens.

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.

Two Successful Cases of PJ Rigid Gas Permealble Contact Lens after Myopic Excimer Laser Photorefractive Keratectomy

To improve visual acuity of patients with myopic regression and corneal haze after myopic excimer laser photorefractive keratectomy(PRK), rigid gas permeable(RGP) lens have been recommended. however, spherical RGP lenses cause problems in some cases. We experienced two patients who had some problems with a spherical RGP lens after PRK, but recovered with PJ lens(Park and Joo type RGP lsens) with two base curves of optical zone depending on native patient's keratometric readings. We examined weekly and a corneal topography monthly. Some problems like superficial punctate erosion and corneal molding by spherical RGP lens were disappeared and central corneas regained their original figures and became to be spherical with the more desirable curvature 3 months after PJ lens fitting. Additionally, there was no complication. With these results, we suggest that PJ lens, newly designed RGP lens, can be a choice of RGP lens to improve a corrected visual acuity without complication in case of the patients performed myopic refractive surgery like PRK.