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Geunyoung Yoon, Seth Pantanelli, Tae Moon Jeong, Scott MacRae; Characterizing optical quality of abnormal eyes using large dynamic range Shack-Hartmann wavefront sensor. Journal of Vision 2004;4(11):94. doi: https://doi.org/10.1167/4.11.94.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Although several studies investigated the aberration of the eye in a normal population, little wave aberration data can be obtained from eyes with abnormal conditions, such as those having keratoconus or penetrating keratoplasty (PK). Since these eyes could get benefit most from developing customized correction methods, the objective of this study is to characterize optical quality of the eye's optics for these abnormal groups.
METHOD: A large dynamic range Shack-Hartmann wavefront sensor was developed to measure the highly aberrated eyes for a large pupil (at least 6 mm in diameter). The modified design, which involves placing a translatable plate in conjugate with the lenslet array, blocks every other spot on the photodetector in a single exposure. All of the spots are collected by translating the plate to reveal previously masked lenslets. The prototype device increases the dynamic range by a factor of two without sacrificing any measurement sensitivity. With this device, the wavefront was measured for 19 keratoconic and 14 PK eyes and compared with the data for normal eyes.
RESULT: All keratoconic subjects except for one possessed negative vertical coma; the magnitude of the aberration was −1.41 ± 1.06 µm (mean ± standard deviation). PK subjects exhibited large amounts of trefoil; however there was no consistency with the sign. Overall, the higher-order variance in both abnormal eye populations accounted for 16% of the total variance, compared to only 1% for normal eyes. Visual benefit calculations for 12 of the keratoconic eyes indicate that they may experience visual benefit improvements ranging between 2 and 10 times what is possible with conventional correction.
CONCLUSION: The large dynamic range Shack-Hartmann wavefront sensor has been successfully developed to characterize the aberrations in two groups of abnormal eyes over a large pupil. By measuring the aberrations in a relatively large population, a more comprehensive understanding of the optical quality in these groups is obtained. Visual performance may be substantially improved with developing customized correction methods, such as customized contact lenses or customized intra-ocular lenses.
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