Comparison of 4 different wavefront analyzers in a model eye with different, known waveplates

Abstract

Abstract: : Purpose:To compare absolute accuracy of four wavefront sensing devices based on different principles Methods:We used four different devices for comparison: the Tracey Visual Function Analyzer (VFA), based on the ray–tracing principle; the Nidek OPD–Scan, based on the dynamic skiascopy principle; the Zeiss Quantum (Quantum), and our custom–built wavefront analyzer, both based on the Hartmann–Shack principle. 4 custom–made waveplates with known higher–order aberrations were measured to verify the accuracy. The waveplates were placed into a custom eye model with a 20 mm achromat (Melles Griot) and an artificial retina (Spectralon). Results:Each instrument was initially measured with the eye model without any waveplate and we found that the higher order Zernike terms were all negligible. This proved that our eye model did not introduce additional aberrations. Subsequently, we placed the different waveplates in our eye model and measured higher order aberrations. No correlation between any of the instruments and the known aberration or between different instruments were observed. To account for eye model induced aberrations we also subtracted the eye model's initial waveaberration measurements from the waveplate measurements. The results were similar. Conclusions:The results suggest that different instruments vary greatly in their ability to determine higher order aberrations. Possible reasons include artifacts introduced by the higher reflectivity of our model retina or centration misalignment. It is recommended that the industry established a set of simple calibration tools for higher order aberration that can be performed by each instrument user.

Keywords: refraction • optical properties • imaging/image analysis: clinical