• Journal of Korean Ophthalmic Optics Society
• /
• v.17 no.4
• /
• pp.373-380
• /
• 2012

Purpose: The present study was performed to investigate a relationship between the stable centrations of spherical RGP lens and aspherical RGP lens on cornea and corneal eccentricity. Methods: Two RGP lenses with different designs were fitted in alignment, steep or flat on total 84 eyes having corneal eccentricity of 0.28~0.78. The stable centration of lenses on cornea was analyzed by taking photographs with a high-speed digital camera. Results: The stable centrations of spherical and aspherical RGP lenses in horizontal direction were decentrated to temporal side. More centration to median side was shown when corneal eccentricity was larger. The difference between the stable centrations of spherical and aspheric RGP lenses according to corneal eccentricity was bigger when the fitting state was flatter. The difference in the stable centrations of aspherical RGP lens was smaller than that of spherical RGP lens regardless of fitting status. The stable centrations of spherical and aspherical RGP lenses in vertical direction were located below corneal apex regardless of fitting status however, there was no significant difference analyzed by the variation of corneal eccentricity. However, there were many cases that RGP lenses were in upper eyelid with increasing corneal eccentricity. Conclusions: The consideration of corneal eccentricity is required for RGP lens fitting and manufacturing aspherical RGP lens since the stable centration of spherical RGP lens as well as aspherical RPG lens' centration was changed depending on corneal eccentricity.

• Journal of Korean Clinical Health Science
• /
• v.4 no.4
• /
• pp.662-670
• /
• 2016

Purpose. Because of a recent increase in use of soft contact lens at younger ages, in the present study, the correlation between corneal eccentricity and radius of curvature and fitting types of contact lens was investigated. Methods. The study evaluated the fitting status of targets through lens centration, push-up test, dynamic lag test and static lag test of lenses usually worn by 49 men and women (98eyes) in their 20s to 30s who put on soft contact lenses. After evaluation, the subjects were classified into 3 categories by fitting status(steep, aligment and flat). The radius of corneal curvature in the naked eyes was measured by using keratometer. Moreover the corneal eccentricity in the nasal side, temporal side, superior side and inferior side was measured by using the device capable of measuring the corneal eccentricity. Results. The radius of corneal curvature and corneal eccentricity of soft lenses worn by subjects were higher in the order of steep fitting and flat fitting, and the higher average corneal curvature radius and corneal eccentricity is intend to be more steep fitting(p=0.051, p=0.052). The corneal eccentricity showed a tendency to nasal fitting type at the higher eccentricity and temporal fitting type at the smaller eccentricity, statistically significant difference was observed(p<0.05). The study showed there were low correlation that nasal and temporal side at steep fitting, superior side at normal fitting and 4side(nasal, temporal, superior, inferior) at flat fitting, therefore when the corneal eccentricity changed the radius of corneal curvature also changed. The corneal eccentricity and the radius of corneal curvature showed statistically significant difference at 4side and each fitting types(p<0.05). Conclusions. The results of this study, the fitting status, of wearer are based on radius of corneal curvature and corneal eccentricity, and if lens fitting would be done considering that, it seems to be useful in a soft contact lens prescription.

• Journal of the Korea Convergence Society
• /
• v.9 no.8
• /
• pp.117-125
• /
• 2018

Aims of this study was to investigate on the actual condition of contact lens wearing after corneal refractive surgery, base curves and diameters of lenses on sale, and to confirm movement of lens and wear patterns when wearing of lenses in the modified cornea. After surgery, 16.5% of the respondents had experience wearing contact lenses. Also, the mostly distributed contact lenses had B.C. 8.6mm and DIA.14.0mm. The corneas of 24 eye after corneal refractive surgery were flat, the lenses moved towards inferior and temporal when wearing the lens. After corneal refractive surgery, contact lens wear may feel uncomfortable may require the detailed description and sophisticated fitting due to the limited type of contact lens. It is thought that convergence will be necessary in the industry and clinical study of contact lenses.

• Journal of Korean Ophthalmic Optics Society
• /
• v.16 no.1
• /
• pp.41-50
• /
• 2011

Purpose: The present study was conducted to compare the centration of RGP lens on cornea when lens was fitted based on keratometric astigmatisms measured by keratometer and the lens centration when fitted by corneal topography. Methods: Thirty eight eyes of 19 male and female in their twenties were applied RGP lens with 9.9 mm of diameter by the keratometric astigmatisms classified by the measurement with a keratometer. Then, lens centrations were estimated using high speed camera and compared with the lens centration when fitted by total keratometric astigmatism using corneal topography. The relationship of the steepest location of cornea and lens centration was further compared. Results: With the rule astigmatism, lens centration was not changed even with the difference in central and total keratometric astigmatisms. When the relationship of the steepest part of cornea measured by corneal topography and lens centration was analyzed, the lens centration in vertical direction was exactly correlated with the steepest part of cornea in 52.3% of subjects. In the case of non-correlation, the steepest part of cornea was mostly upper part of cornea, however, lens centration was located on lower part of cornea. The lens centration in horizontal direction was exactly correlated with the steepest region of cornea in 65.6% of subjects. In non-correlated case, the difference in cornea curvatures between the steepest and the flattest parts was smaller than 0.05 mm in 76.9% of subjects. Conclusions: From these results, we conclude that corneal topographic patterns may more contribute the centration of RGP lens on cornea than the difference in central and total keratometric astigmatisms.