Abstract
Purpose :
Clinicians commonly evaluate lens centration relative to the visible iris (i.e., limbus), providing an estimation of lens centration relative to the corneal center. However, the axis of importance for vision is not the axis passing through the corneal center (videokeratoscopic axis), but rather the axis passing through the pupil center. The purpose of this study was to characterize the on-eye centration of current commercially available, non-stabilized soft contact lenses in a clinical population.
Methods :
220 non-diseased, adult eyes were videoed in normal illumination (~133cd/m2) while wearing their habitual spherical soft contact lenses. 60 frames were acquired over 10 seconds. Custom validated image analysis software was used to calculate measurements of pupil diameter, visible iris diameter, and the locations of the contact lens center, pupil center, and visible iris center.
Results :
The mean±standard deviation pupil and corneal diameters for all subjects were 3.84±0.83 mm and 11.97±0.48mm, respectively. Averaged across all eyes, the mean [95% confidence interval] pupil center was located slightly nasally (0.280 mm [0.260, 0.300]) and superiorly (0.075 mm [0.047, 0.103]) relative to the corneal center. Consistent with clinical observations, the contact lenses centered accurately relative to the corneal center both nasally (0.040 mm [0.010, 0.069]) and inferiorly (-0.014 mm [-0.056, 0.028]). However, regardless of eye, the contact lens was significantly (p<0.001) decentered relative to the pupil center both temporally (-0.231 mm [-0.264, -0.199]) and inferiorly (-0.082 mm [-0.121, -0.043]).
Conclusions :
Evaluating the lens center relative to the pupil center may prove most beneficial in predicting the optical impact of lenses on eye. The spherical contact lenses evaluated in this study centered temporally and inferiorly from the primary line of sight (pupil center). An exploratory analysis of a data subset indicated that contrary to some previous reports, there was no significant difference in lens centration between single vision and multifocal lenses of the same design. Most spherical lenses contain spherical aberration which when decentered induces coma in direct proportion to the amount of lens decentration. Incorporating knowledge of the lens centration relative to the pupil center into a lens design may provide enhanced vision for wearers.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.