Validation of an off-eye contact lens Shack-Hartmann wavefront aberrometer

To evaluate the ability of a commercially available single pass Shack-Hartmann aberrometer to evaluate contact lens aberrations.

Accuracy of second-order aberration measurements was verified by measuring a series of precision calibration lenses, spectacle lenses, and contact lenses. Power measurements were compared to those expected by an independent measurement or those provided by the lens manufacturer. Accuracy of third-order aberrations was verified by systematically decentering a lens with known amounts of spherical aberration and comparing the magnitude of induced coma to that of optical theory. Fourth-order aberration accuracy was verified by comparing measured longitudinal spherical aberration values to those expected by ray tracing based on the lens design. Accuracy of lower- and higher-order aberrations was verified for measurements of lenses taken in air and within a saline-filled wet cell. Repeatability was also assessed by comparing repeated measurements of the wet cell and lens in a wet cell, before and after manipulation of that cell.

In all cases, measured values closely matched the expected values, generally exhibiting errors of <1%.

The instrument demonstrates good accuracy and repeatability in measuring second-, third-, and fourth-order aberrations of contact lenses and provides the industry with an instrument for evaluating the ex vivo optical characteristics of contact lenses.