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KMID : 1159320070090030301
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Korean Journal of Vision Science
2007 Volume.9 No. 3 p.301 ~ p.316
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The comparative analysis of the changes in refractive error and corneal shape with two different diameter of Orthokeratology contact Lens
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Kim Mi-Young
Oh Hyun-Jin
Byun Jang-Won
Nam Sang-Hoon
Mah Ki-Choong
Sim Sang-Hyun
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Abstract
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To compare and analyze the effects change in diameter of orthokeratology contact lens has on refractive error and corneal shape, 16 healthy individuals with no eye diseases were fitted with two different types of overnight orthokeratology contact lens with different diameters(10.0 mm and 11.2 mm) and auto refractometer, auto keratometry, subjective refraction, and ORBSCAN topography/pachymetry were performed for each individual before wearing the contact lens, 1 day after wear, and 7 days after wearing the contact lens.
In the lens with different diameters, there were no differences in improvement of visual acuity or in reduction of refractive error measured by subjective refraction, and significant difference was found in refractive error measured by auto refractometer(t = -3.573, p = 0.001). Corneal astigmatism decreased in lens with greater diameter, and increased in lens with smaller diameter, which showed a significant difference(t = -2.794, p = 0.008). The change in mean K-reading(t = -3.586, p = 0.001), flat K-reading(t = -5.452, p = 0.000), and steep K-reading(t = -5.117, p = 0.000) measured using autokeratometer at one week after wearing the lens was flatter in the lens with greater diameter. Corneal thickness decreased in the central region and increased in the periphery which showed statistically significant differences(t = 3.149, p = 0.001). The width of treatment zone was slightly wider in the lens with greater diameter than in lens with smaller diameter(t = 2.498, p = 0.013).
From the above results, although lens with 11.2 mm diameter did not have differences in effect of improving visual acuity or decreasing astigmatism compared to lens with 10.0 mm diameter, with changes in corneal curvature and increase in the region of pressure, it is believed to be able to provide stable myopia reduction effect and further studies that can be applied in the fitting process for solving clinical problems are anticipated.
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KEYWORD
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Orthokelatology contact lens, Corneal topography, Corneal thickness, Corneal radius of curvature, Treatment zone, Orbscan Pachymetry System
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