각막지형 및 주시각도에 따른 멀티포컬 콘택트렌즈의 편심 및 근거리 대비시력 변화의 관계

Purpose: In this study, the changes in lens decentration and near visual acuity according to the corneal topography and gaze angle were investigated while wearing aspherical center near multifocal soft contact lenses (hereinafter multifocal lenses). Methods: Corneal types of 30 eyes of men and women in their 20s with corrected visual acuity of 0.8 or higher were classified into symmetric and asymmetric bow-ties with superior and inferior steep, respectively, and wore center near multifocal lenses made of omafilcon A, etafilcon A, and nesofilcon A. Subsequently, the gaze angle was changed 15o and 40o downward from the primary gaze. At that time, the decentration of the multifocal lens was measured, and area ratio of the optical zone of the lens covering the participant's pupil at each gaze angle was calculated using Photoshop by dividing it into an add zone and a distance zone. After measuring near contrast visual acuity under photopic and mesopic conditions, the relationship among the lens decentration and changes in near contrast visual acuity between the corneal topography and the lens types according to gaze angles was analyzed. Results: In all down gaze conditions, significant upward decentration of the multifocal lens was observed in symmetric bow-tie typed cornea than in asymmetric bow-tie typed cornea. At 40o down gaze, there was an interaction between corneal topography and lens type in the difference value of near low contrast visual acuity with primary gaze under photopic condition, and there was a statistically significant interaction between corneal topography and lens type in the difference of near high and low contrast visual acuity with primary gaze under mesopic condition. It was also found that the ratio of pupil covered by the add zone of multifocal lenses did not correlate well with near contrast visual acuity. Conclusions: Based on these results, it can be suggested that corneal topography should be considered when fitting a multifocal lens since symmetric bow-tie typed cornea showed large lag depending on the near gaze directions after wearing a multifocal lens, while the asymmetric bow-tie/inferior steep and asymmetric bowtie/superior steep typed corneas showed differences in near contrast visual acuity according to gaze habits and lens design.