A precision, large stroke (nearly 1 cm) scanning system was designed, built, and calibrated for micromachining of ophthalmic materials including hydrogels and cornea (excised and in vivo). This system comprises a flexure stage with an attached objective on stacked vertical and horizontal translation stages. This paper outlines the design process leading to our most current version including the specifications that were used in the design and the drawbacks of other methods that were previously used. Initial measurements of the current version are also given. The current flexure was measured to have a 27 Hz natural frequency with no load.

Uncorrected refractive errors are a major cause of amblyopia, which interrupts social functioning and academic performance in children [1]. It is estimated that over one billion people suffer from uncorrected refractive errors worldwide [2,3]. The incidence rate of amblyopia caused Purpose: To compare refractive error measured by hand-held wavefront aberrometers with postcycloplegic autorefraction (AR) and cycloplegic refraction (CR). Methods: The medical records of patients who received refractive measurements using the wavefront aberrometer, postcycloplegic AR, and CR between January 2014 and January 2016 were retrospectively analyzed. The mean differences, 95% confidence intervals, and limits of agreement (LOA) were calculated for the refractive vector components (M, J 0 , and J 45). Results: Fifty-one patients (9.0 ± 5.5 years, male 41.2%) were enrolled in this study, and only the right eye of each was included. Refractive errors ranged from-9.25 to +7.25 diopters (D) for spherical equivalent (median, 0.75 D). The M component was not significantly different among the three methods (p = 0.080). However, the J 0 vector component was significantly different (p < 0.001). After post hoc analysis, the wavefront aberrometer obtained more positive values for J 0 compared to the other methods. The J 45 component was not significantly different among the three methods (p = 0.143). The mean difference between the wavefront aberrometer and postcycloplegic AR was-0.115 D (LOA,-1.578 to 1.348 D) for M, 0.239 D (LOA,-0.371 to 0.850 D) for J 0 , and-0.015 D (LOA,-0.768 to 0.738 D) for J 45. The mean difference between the wavefront aberrometer and CR was-0.220 D (LOA,-1.790 to 1.350 D) for M, 0.300 D (LOA,-0.526 to 1.127 D) for J 0 , and-0.079 D (-0.662 to 0.504 D) for J 45. Conclusions: The wavefront aberrometer showed good agreement with postcycloplegic AR and CR in spherical equivalents, but tended to produce slightly myopic results. The wavefront aberrometer also overestimated with-the-rule astigmatism. Therefore, we recommend that the device be used for estimations of refractive error, which may be useful for patients who have postural difficulties, live in undeveloped countries, or are bedridden.

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