Effect of Base Curve on Silicone Hydrogel Contact lens Fitting Characteristics and Comfort

Abstract

Purpose : To compare the fitting assessment and subjective comfort according to the base curves of silicone hydrogel lens. Methods : Thirty adults (60 eyes, mean age: 21.9 years) who had no ocular disease and no problem in wearing contact lenses were included. Contact lens fittings were performed with empirical and trial fitting methods. ln empirical fitting. base curve of contact lenses were selected based on K–reading (fitting contact lens with 8.5 mm base curve in the case of steeper than 7.8 mm. 9.0 mm base curve in the case of flatter than 7.8 mm), and in trial fitting, two base curves were fitted by a double blind method. The fitting characteristics were assessed with centration, movement, lag, push-up test and keratometer mire. The subjective comfort was evaluated through questionnaires with Likert 5-point scale. Results : It was shown that 91.67% of the subjects was acceptable to base curve determined by empirical fitting. However, 33.33% of steep curve group showed ideal fitting with 9.0 mm base curve and 25% of flat curve group showed ideal fitting with 8.5 mm base curve, and empirical and trial fitting showed 71.67%, 100% in success rate, respectively. It was appeared that 63.33% of subjects felt no difference in the comfort sensation of contact lenses with different base curves, but the comfort sensation with the 8.5 mm base curve (3.53 points) was significantly higher than 9.0 mm base curve (2.75 points), (t=4.528, p<0.001) and 27.78% of a flat cornea group felt comfortable with steeper fitting. Conclusion : In order to determine the base curve of silicone hydrogel contact lenses, it is suggested that evaluating the fitting condition is more important than subjective fitting condition of the wearer or empirical determination.