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D Robert Iskander, Pawel Wachel; Practical limits of eye surface profilometry. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2475.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the practical limits of a new anterior eye height measuring device based on the principle of profilometry (Eye Surface Profiler, Eaglet Eye, Netherlands) and to establish its accuracy in measuring a range of different types of surfaces.
An algorithm that simulates the images resulting from the projection of the two grid patterns in eye surface profiler has been developed. Spherical (R = 8 mm and R =12 mm), aspherical with astigmatism (Rx=8 mm, Ry = 7.5 mm, Q = -0.26), and a smoothed (10th radial order Zernike polynomial approximation) bi-curve surface resembling and eye with an inner spherical part (R_in=8 mm) and outer spherical part (R_out=12 mm) have been chosen for the evaluation of the instrument. Accuracy of the surface estimation in terms of the root mean square (RMS) error was considered. Several important parameters of the Eye Surface Profiler, such as the carrier frequency, image quantization level, sensor size, carrier frequency inaccuracy, processing type, and level and type of noise were studied.
In the majority of cases and ranges considered in the study the instrument algorithm achieved sub-micron accuracy. A clear advantage of the double projection of the system in comparison to a single projection processing type was shown, where in the latter case the RMS was 2 orders higher than in the case of the former.
The algorithms used in eye surface profilometry achieve similar levels of accuracy used in keratoscopy based instruments with an unprecedented extension of the measuring coverage.
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