ARVO 2023: Improving on-eye centration of soft contact lenses

clinicians generally evaluate lens centration in relation to the visible iris, which provides an estimate of lens centration relative to the corneal center. (Image Credit: AdobeStock/Africa Studio)

Researchers from the School of Optometry, Indiana University, Bloomington, reported that changing how clinicians evaluate lens centration on the eye may be beneficial for improving vision. They suggested that evaluating the lens center relative to the pupillary center may prove most beneficial in predicting the optical impact of the lenses on the eye.

Grace Walther, first author of the study, described the findings at the Association for Research in Vision and Ophthalmology annual meeting.

She explained that clinicians generally evaluate lens centration in relation to the visible iris, which provides an estimate of lens centration relative to the corneal center. However, she noted, the axis of importance for vision is not the axis passing through the corneal center (videokeratoscopic axis), but rather the axis passing through the pupillary center.

The research team conducted this study to characterize the on-eye centration of current commercially available, non-stabilized soft contact lenses (CLs) in a clinical population.

A total of 220 healthy adult eyes were videoed in normal light while wearing spherical soft CLs. Image analysis software then calculated the pupillary diameter and visible iris diameter and identified the locations of the CL center, pupillary center, and visible iris center.

The authors reported that the mean ± standard deviation pupillary and corneal diameters were 3.84±0.83 mm and 11.97±0.48 mm, respectively.

When they averaged the pupillary measurements in all eyes, the mean pupillary center was slightly nasal (0.280 mm [0.260, 0.300]) and superior (0.075 mm [0.047, 0.103]) to the corneal center.

“Consistent with clinical observations, the CLs were centered accurately relative to the corneal center nasally (0.040 mm [0.010, 0.069]) and inferiorly (-0.014 mm [-0.056, 0.028]). However, regardless of the eye, the CLs were significantly (p<0.001) decentered relative to the pupillary center temporally (-0.231 mm [-0.264, -0.199]) and inferiorly (-0.082 mm [-0.121, -0.043]),” they pointed out.

Evaluating the lens center relative to the pupillary center may be more beneficial for predicting the optical impact of the lenses on the eye, the authors suggested.

The authors commented, “The spherical CLs evaluated in this study were centered temporally and inferiorly from the primary line of sight (pupillary 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 aberrations that when decentered induce coma in direct proportion to the amount of lens decentration. Incorporating this knowledge of the lens centration relative to the pupillary center into a lens design may provide enhanced vision for wearers.”