Comparison of internal anterior chamber diameter measured with ultrabiomicroscopy with white-to-white distance measured using digital photography in aphakic eyes.

Purpose: Measuring the anterior chamber diameter (AC) is important both for diagnostics and before ocular surgery. In clinical practice, horizontal AC diameter is usually estimated on the basis of measurements of corneal diameter (so-called white-to-white [WTW] distance). The usual method for selecting an appropriate size for an AC lens is to add 1 mm to WTW measurement. The purpose of this study was to compare AC diameter measured using ultrasound biomicroscopy (UBM) with WTW distance measured using digital photography in aphakic eyes.

Methods: The data were gathered prospectively from a nonrandomized consecutive series of aphakic patients. The examined group consisted of 23 eyes of 23 adult patients, mean age 71.17 years. WTW diameter was measured in the 3 o'clock and 9 o'clock meridian on a digital photograph. Internal horizontal AC diameter measurements were performed in the 3 o'clock and 9 o'clock meridian with the Sonomed Ultrabiomicroscopy device with a 50-MHz probe.

Results: Mean horizontal WTW diameter measured using digital photographs was 11.65+/-0.38 mm and mean horizontal internal AC diameter measured using UBM was 13.53+/-0.83 mm. A significant difference in mean WTW diameter measured using digital photography and UBM was found (Mann-Whitney U test, p<0.05). There was a significant correlation between these values (Spearman=0.70, p<0.001).

Conclusions: In order to obtain good and precise measurements of internal AC diameter, a method of direct visualization of the intraocular structures should be used. Despite the limits of a small case series, our results support the use of UBM technique for preoperative evaluation of the internal AC diameter and AC intraocular lens sizing in aphakic eyes.