Objective measurement of accommodative biometric changes using ultrasound biomicroscopy

Abstract

PURPOSE To demonstrate that ultrasound biomicroscopy (UBM) can be used for objective quantitative measurements of anterior segment accommodative changes. SETTING College of Optometry, University of Houston, Houston, Texas, USA. DESIGN Prospective cross-sectional study. METHODS 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. RESULTS 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 (P < .0001) linearly correlated with accommodative stimulus amplitudes. 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. CONCLUSIONS 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.

Non-invasive measurements of the dynamic changes in the ciliary muscle, crystalline lens morphology, and anterior chamber during accommodation with a high-resolution OCT

“…The results obtained in this study show the same tendency as those obtained previously [1,4,[22][23][24], in which the lens thickness increased with vergence. At the same time, it has been reported that the posterior lens surface might move backwards with accommodation, because the increase in lens thickness with accommodation is higher than the decrease in the ACD [20].…”

Prediction of accommodative optical response in prepresbyopic subjects using ultrasound biomicroscopy

“…A similar study of 26 young subjects (8 men, 18 women), aged 21 to 36 years (mean age 24.15 ± 3.03 years) was performed previously. 12,15 A comparison of data from young and prepresbyopic subjects will be presented here.…”

“…12 Briefly, the subject lay supine, looking up, with the head stabilized with a gel headrest. Immediately in front of the viewing eye was a beam splitter oriented at 45 degrees.…”

“…Correction factors were calculated from the calibration surfaces to correct the measured anterior and posterior lens radii of curvature and measurements. 12 …”

“…At present, it is not possible to objectively measure the accommodative optical and biometric changes with a single clinical instrument. Previous studies 12–14 report that the accommodative optical and biometric changes are linearly related. Using these linear relationships, a study 15 of young human subjects showed that the accommodative optical response could be predicted from UBM-measured anterior segment biometry parameters with standard deviations of less than 0.50 diopter (D).…”