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Editors Selection IGR 20-3

Angle assessment: SPAC – case finding AC

Comment by Gus Gazzard on:

20122 Case finding of angle-closure glaucoma in public health examination with scanning peripheral anterior chamber depth analyzer, Kashiwagi K; Tsukahara S, Journal of Glaucoma, 2007; 16: 589-593

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Angle closure glaucoma (PACG) has become increasingly recognised as a major cause of preventable blindness in the World, due largely to high preva-lence rates in the very populous Asian countries (Quigley H, Br J Ophthalmol 2006; 90: 262-267). Yet unlike open-angle glaucoma, for which Burr et al. (Health Technol Assess 2007; 11: iii-iv, ix-x, 1-190) have recently shown, large-scale population screening is not cost-effective, true prevention may be possible for PACG. It is likely that early intervention ‐ by laser iridotomy or lens extraction ‐ may prevent progression from angle closure suspect (narrow angle without sequelae) through primary angle closure (signs of peripheral anterior synechiae and/or raised intra-ocular pressure) to glaucomatous optic neuropathy (Nolan W, et al. Br J Ophthalmol 2000; 84: 1255-1259). Confirmation of such a strategy and details such as the ideal treatment threshold must await large population-based trials, yet they will rely upon robust technician operated screening tests to be viable.

Kashiwagi et al. (1177) have developed a novel non-contact de-vice ‐ the 'Scanning Peripheral Anterior Chamber Depth Analyzer' (SPAC) ‐ for assessment of the limbal anterior chamber depth. In their latest study they assess the effectiveness of the SPAC as used by technicians in screening 535 Japanese subjects over 40 years old.

SPAC identifies cases needing further detailed examination, such as gonioscopy

They identified cases needing further detailed examination such as gonioscopy, using anterior chamber depth values determined to give high sensitivity in earlier studies. Thirty-nine subjects were eventually found to have PACS, PAC or PACG but unfortunately, since not all those screened had a definitive examination, it is not possible to derive false negative rates. Nonetheless the SPAC clearly holds promise as a well-tolerated, affordable and robust non-contact device that can be readily interpreted by non-ophthalmologists. Future versions should improve further upon sensitivity and specificity values that already compare well with previous contenders for potential screening devices.

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