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Study: On-eye factors may vary SCL optics from expected values
A study examining the on- and off-eye optical performance of hydrogel and silicone hydrogel soft contact lenses found that the major difference between the on-eye lens optics and the manufacturers' specifications is caused by eye-lens interactions, not lens errors.
The researchers measured monochromatic aberrations in the lenses on-eye and off-eye within a wet cell.
No significant differences were found between on-eye and off-eye sphere and spherical aberration values for both types of lenses; however, high plus-power lenses exhibited a significantly lower sphere power on-eye than expected from both measured powers off-eye and lens specifications.
Longitudinal spherical aberration varied with lens power in the hydrogel lenses, as expected from geometric optics theory. However, longitudinal spherical aberration measurements on- and off-eye deviated significantly from that expected.
These variances could either be caused by lens flexure or a tear lens forming behind the soft contact lens, according to the study authors