Objective measurement of accommodative biometric changes using ultrasound biomicroscopy

Abstract

To demonstrate that ultrasound biomicroscopy (UBM) can be used for objective quantitative measurements of anterior segment accommodative changes. College of Optometry, University of Houston, Houston, Texas, USA. Prospective cross-sectional study. Anterior segment biometric changes in response to 0 to 6.0 diopters (D) of accommodative stimuli in 1.0 D steps were measured in eyes of human subjects aged 21 to 36 years. Imaging was performed in the left eye using a 35 MHz UBM (Vumax) and an A-scan ultrasound (A-5500) while the right eye viewed the accommodative stimuli. An automated Matlab image-analysis program was developed to measure the biometry parameters from the UBM images. The UBM-measured accommodative changes in anterior chamber depth (ACD), lens thickness, anterior lens radius of curvature, posterior lens radius of curvature, and anterior segment length were statistically significantly linearly correlated with accommodative stimulus demands. Standard deviations of the UBM-measured parameters were independent of the accommodative stimulus demands (ACD: 0.0176 mm; lens thickness: 0.0294 mm; anterior lens radius of curvature: 0.3350 mm; posterior lens radius of curvature: 0.1580 mm; and anterior segment length: 0.0340 mm). The mean difference between the A-scan and UBM measurements was -0.070 mm for ACD and 0.166 mm for lens thickness. Accommodating phakic eyes imaged using UBM allowed visualization of the accommodative response, and automated image analysis of the UBM images allowed reliable, objective, quantitative measurements of the accommodative intraocular biometric changes. Neither author has a financial or proprietary interest in any material or method mentioned.