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PURPOSE: Clinical accommodation testing involves measuring either accommodative optical changes or accommodative biometric changes. Quantifying both optical and biometric changes during accommodation might be helpful in the design and evaluation of accommodation restoration concepts. This study aims to establish the accuracy of ultrasound biomicroscopy (UBM) in predicting the accommodative optical response (AOR) from biometric changes. METHODS: Static AOR from 0 to 6 diopters (D) stimuli in 1-D steps were measured with infrared photorefraction and a Grand Seiko autorefractor (WR-5100 K; Shigiya Machinery Works Ltd., Hiroshima, Japan) in 26 human subjects aged 21 to 36 years. Objective measurements of accommodative biometric changes to the same stimulus demands were measured from UBM (Vu-MAX; Sonomed Escalon, Lake Success, NY) images in the same group of subjects. AOR was predicted from biometry using linear regressions, 95% confidence intervals, and 95% prediction intervals. RESULTS: Bland–Altman analysis showed 0.52 D greater AOR with photorefraction than with the Grand Seiko autorefractor. Per-diopter changes in accommodative biometry were: anterior chamber depth (ACD): −0.055 mm/D, lens thickness (LT): +0.076 mm/D, anterior lens radii of curvature (ALRC): −0.854 mm/D, posterior lens radii of curvature (PLRC): −0.222 mm/D, and anterior segment length (ASL): +0.030 mm/D. The standard deviation of AOR predicted from linear regressions for various biometry parameters were: ACD: 0.24 D, LT: 0.30 D, ALRC: 0.24 D, PLRC: 0.43 D, ASL: 0.50 D. CONCLUSIONS: UBM measured parameters can, on average, predict AOR with a standard deviation of 0.50 D or less using linear regression. UBM is a useful and accurate objective technique for measuring accommodation in young phakic eyes. [ J Refract Surg. 2015;31(4):266–273.]