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B.-U. Seifert, S. Schramm, P. Bessler, P. Schikowski, K. S. Kunert; Clinical Validation of a Modified Wavefront Analyzer - Preliminary Results. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3948.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the influence of modifications made to a commercially available wavefront analyzer (WASCA, CZM AG). Modifications aim for combined measurements of aberrations and scatter of the eye using one integrated device based on Hartmann-Shack technology. To increase the amount of straylight imaged onto the sensor a confocal pinhole, typically used to suppress corneal reflections and to improve spot imaging, has to be extended. To reduce effects of corneal reflections the instrument is adjusted off-axis. Both pinhole extension and off-axis adjustment hold the capability of altering the aberration measurements which has to be investigated.
Two similar wavefront analyzing devices (WAD) where introduced. WAD1 featured the original confocal pinhole whereas pinhole of WAD2 was extended to 8 mm in diameter. To suppress corneal reflections the optical axis of the device was shifted to the temporal side. Measurements where performed on 5 subjects (36.2+/-8.1 years, -1.10+/-1.55 dpt) on both eyes. Each eye underwent the following measurement modes: WAD2 off-axis, WAD1 off-axis, WAD1 on-axis yielding 10 samples per eye and per mode. Zernike coefficients up to 4th order where analyzed. Samples where tested for normal distribution (p<0.05). T-Test and f-Test were performed to assess comparability and reproducibility regarding different pinhole size and axis shift.
Temporal shift of the device axis resulted in a significant difference of 4 Zernike coefficients in total (p<0.05, left: 3, right: 1). Temporal shift in conjunction with an extended pinhole further increased it to a total of 10 Zernike coefficients of significant difference (p<0.05, left: 7, right: 3). F-test across the measurement modes showed no significant difference in standard deviation.
Despite the limited number of subjects there is at least some evidence that modifications intended for scatter measurement in the eye by conventional wavefront analyzer affect the aberration measurement characteristics. It can be concluded that for simultaneous assessment of aberration and scatter within one single device a sequential procedure is advisable to ensure optimum conditions for each mode. A currently on-going study will help to overcome limitations due to population distribution and size.
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