Anterior Chamber Depth Measurement as a Screening Tool for Primary Angle-closure Glaucoma in an East Asian Population

Abstract

Setting: Rural and urban locations in the Hö vsgö l and Ö mnö gobi provinces, Mongolia. Participants: Nine hundred forty-two (94.2%) of 1000 individuals in Hö vsgö l (1995) and 775 (96.9%) of 1000 individuals in Ö mnö gobi (1997) aged 40 years or older were examined. Main Outcome Measures: Anterior chamber depth was measured by optical pachymetry, slitlamp-mounted Amode ultrasound, and handheld ultrasound. Gonioscopy was used to detect occludable angles, defined as one in which the trabecular meshwork was visible for less than 90°of angle circumference. Primary open-angle glaucoma was diagnosed in subjects with an occludable angle and glaucomatous optic neuropathy with visual morbidity. The area under the curve in a receiver operating characteristic plot was used to compare test performance. Results: Optical pachymetry outperformed the slitlampmounted ultrasound method of anterior chamber depth measurement (area under the curve, 0.93 and 0.90, respectively; z test, P = .001). Handheld ultrasound (area under the curve, 0.86) was inferior to optical measurement (z test, P = .001) but did not differ significantly from slitlamp ultrasound (z test, P = .06). The optical method gave sensitivity of 85% and specificity of 84% at a screening cutoff of less than 2.22 mm for detecting occludable angles. Conclusions: Measurement of axial anterior chamber depth can detect occludable angles in this Asian population and therefore may have a role in population screening for primary angle-closure glaucoma.

The genetic mechanisms of primary angle closure glaucoma

“…[35][36][37][38] A small anterior segment represents a major risk factor with limbal and axial anterior chamber depth being the traits most strongly correlated with ACG. [39][40][41] In eyes with hyperopia or shallow anterior chamber depth, the iris is repositioned so that its anterior movement during dilation blocks the iridocorneal angle. This can lead to an acute entrapment of aqueous fluid behind the iris and a rapid increase in IOP.…”

Usefulness of peripheral anterior chamber depth assessment in glaucoma screening

“…5 On the other hand, Congdon et al 7 reported that peripheral slit beam tests such as that of van Herick do not correlate with findings obtained using a gonioscope as well as ultrasonic examination. Judging from the results obtained in this study and those of previous reports, however, van Herick's method is considered to be effective as a screening method for glaucoma patients.…”

“…6,8,9 However, there are divergent opinions regarding the usefulness of peripheral anterior chamber depth measurement, 1,7 and there have also been reports indicating the usefulness of central anterior chamber depth measurement. 5 Consequently, a definite conclusion has yet to be reached concerning the usefulness of peripheral anterior chamber depth measurement. There are also few reports describing the usefulness of peripheral anterior chamber depth measurement in Japanese.…”

“…Studies have been conducted regarding the manner by which patients who are at risk of the occurrence of ACG can be detected. Although the central anterior chamber depth has been reported to be useful in the detection of ACG eyes, 5 it is difficult to use ultrasonic devices in the screening because the test using those devices cannot be performed without touching the cornea. Although gonioscopy is considered to be the most effective diagnostic method, it is subjective and cannot be performed without touching the cornea, and considerable skill and experience are required in making an assessment.…”

Finding cases of angle-closure glaucoma in clinic setting using a newly developed instrument

“…13,[17][18][19][20][21] Devereux et al 18 reported a sensitivity of 77% and a specificity of 83% in a study that used a slitlamp mounted ultrasound ACD measurement system. Congdon et al 17 reported a sensitivity of 88% and a specificity of 92% using ultrasonography in combination with tonography.…”