Purpose:This study aimed to investigate the geometric center position of soft contact lenses and the influence of the scleral shape on lens position.
Methods:In this study, the geometric center of soft contact lenses were marked with a white cross image. The lenses had an overall diameter 14.5 (mm), and were prism ballasted. The lenses were applied to 60 healthy eyes of 30 subjects (16 male, and 14 female). The mean ± SD age of the subjects was 25.5 ± 3.03 years, and spherical equivalent was (-1.91±1.82 (D)). Vertical and horizontal lens position was measured from the visual axis to the optical center of the lens with the Medmont E300 Corneal Topographer. Scleral sagittal height at a chord of 14.50 mm was measured in eight meridians with Precision Ocular Metrology, LLC sMap3D.
Results:The horizontal contact lens mean decentration was 0.81± 0.35 (mm) temporally in the right eye and 0.67 ± 0.31(mm) temporally in the left eye. The vertical decentration mean was 0.59 ± 0.38 (mm) superiorly in the right eye, and 0.56 ± 0.35 (mm) superiorly in the left eye. The contact lens decentered temporally in both eyes for all 30 subjects. Vertically, the lenses decentered superiorly in 55 eyes and stayed centered in 5 eyes. The lens decentration was not statistically significantly different between the right and left eyes (F= 3.308, P=.079, ES= 0.471). The scleral sagittal height varied between the eight primary segments of the sclera (90°, 45°, 0°, 235°,270°, 315°,180°,135°), and there was a statistically significant difference between the right and left eyes (F= 4.230, P
Conclusions: Soft contact lenses were frequently decentered temporally and superiorly in the primary gaze. The scleral shape was asymmetrical and was not associated with lens decentration in this study.
Keywords: Soft contact lenses, decentration, sagittal height (SAG), scleral shape