Primary angle-closure glaucoma and population screening

[caption id="attachment_5779" align="alignnone" width="750"] Gus Gazzard MD study on population screening[/caption]   Primary angle-closure glaucoma would be an ideal candidate for population screening using a telemedicine approach, were it not for the lack of a remote means of diagnosing the condition by non-clinicians, according to Gus Gazzard MD, FRCOphth, Moorfields Eye Hospital, London, UK. “We have a spectrum of disease which is eminently treatable, and at various stages preventable, but we’ve got far too few ophthalmologists to screen such a large population by any traditional form of examination,” Dr Gazzard told the 12th European Glaucoma Society Congress in Prague. He noted that, although it is much less common, angle-closure glaucoma outstrips primary open-angle glaucoma in terms of global blindness. That is despite the availability of safe, proven interventions that can prevent the disease from occurring and can also prevent the early stages of disease from proceeding on to further visual loss once it has become established. The potential benefit of a preventive approach has been demonstrated in a paired-eye trial carried out in Singapore, which showed that only 20 primary angle-closure suspects would need to undergo prophylactic iridotomy in order to reduce by half the number progressing on to more advanced disease. Similarly, the EAGLE trial has shown that lens extraction in patients with angle-closure or angle-closure glaucoma can reduce the need for subsequent glaucoma surgery and medication. GONIOSCOPY PROBLEM The problem with applying these findings to population screening is that the diagnosis of angle-closure depends on the detection of iridotrabecular contact through gonioscopic examination. Gonioscopy is unsuited as a technique for remote examination, as it requires training and experience and an expensive clinician. “We need an accurate, trained technician-based test that can detect iridotrabecular contact, so we can go out and find those individuals who need gonioscopy,” Dr Gazzard said. He noted that studies conducted in public optometric practices in the UK, China and Mongolia have shown that traditional techniques, such as the oblique flashlight test and limbal anterior chamber depth measurements, have too low a specificity for screening large populations on a systematic basis. The same has been shown to be true with more advanced technologies like Scheimpflug and ultrasound biomicroscopy, and anterior segment optical coherence tomography imaging. However, many companies are working on developing technologies that can detect the presence and extent of iridotrabecular contact in an automated fashion. Research has identified novel parameters in angle-closure disease such as lens vaulting and anterior chamber volume, which may have predictive value for angle-closure. “Through the use of complex computer algorithms that are currently being developed, it may be possible to combine those measurements to identify cases for referral for gonioscopic examination,” Dr Gazzard said. Gus Gazzard: gusgazzard@gmail.com

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