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Editors Selection IGR 10-3
Examination methods: Anterior chamber width
Comment by David Friedman on:
11771 Anterior chamber width measurement by high-speed optical coherence tomography, Goldsmith JA; Li Y; Chalita MR et al., Ophthalmology, 2005; 112: 238-244
Goldsmith et al. (40) report on the use of a prototype anterior segment optical coherence tomography device for imaging across the entire anterior chamber. The high speed of image acquisition (4,000 scans per second) using a wide field rectangular scanning geometry along with real-time video display of the image allows for more accurate assessment of the entire anterior chamber. The axial resolution is 19 microns, and the transverse resolution 54 microns. The authors enrolled both eyes of twenty volunteers to determine the anterior chamber width (from angle recess to angle recess in the horizontal meridian), the anterior chamber depth (ACD), and the amount of crystalline lens anterior to the line connecting the angle recesses (referred to as the lens vault), and compared the finding to standard white-to-white (WTW) corneal diameter measurements made clinically along the same meridian. The authors report results using a manual image analysis which requires the grader to identify the apex of the angle recess, but state that they have developed an automated algorithm that performs even better than was found in this study. Nevertheless, reproducibility of the anterior chamber width was good, with a coefficient of variation from of 1%. The OCT measurements correlated well with the WTW measurements. While the authors argue that this approach may yield better lens selection in phakic eyes undergoing anterior chamber IOL placement for refractive purposes, this will need to be verified in clinical studies. Nevertheless, this rapid acquisition of precise images of the entire anterior segment will be a tremendous tool in our understanding of the mechanisms of angle-closure glaucoma. The OCT device described in this article will allow measurements of lens-iris diaphragm changes in response to stimuli, as well as over time. In addition, more detailed analysis of the entire morphology of the anterior segment, as opposed to only looking at the angle, may lead to better prediction of which individuals are at highest risk of angle closure.
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