Angle-closure: From suspicion to certainty

While primary open-angle glaucoma (POAG) affects nearly three times as many people worldwide compared with primary angle-closure glaucoma (PACG), PACG accounts for half of the total cases of glaucoma-related blindness. This information underscores the importance of recognising that PACG develops as a progression condition in eyes with angle-closure, and of identifying and taking care of patients with angle-closure, said John Thygesen MD in his delivery of the ESCRS Glaucoma Day 2016 Keynote Lecture, entitled ‘Angle-closure: from suspicion to certainty’. Dr Thygesen, Copenhagen University Hospital, Denmark, introduced his topic with two key messages. First, POAG is a diagnosis of exclusion. “That means gonioscopy must be done to exclude chronic angle-closure,” he said. Second, most cases of angle-closure are asymptomatic. Therefore, blindness develops in the setting of chronic angle-closure. According to a consensus statement from The Global Glaucoma Network, evaluation of limbal anterior chamber depth may be an appropriate screening test for angle-closure. Gonioscopy, however, is essential for diagnosis and treatment, and Dr Thygesen emphasised that the examination should be performed in a nearly dark room and using both a Goldmann lens and an indentation lens. Treatment decisions for eyes with PAC/PACG should be based on classification using the newer classification system from the International Society for Geographical and Epidemiological Ophthalmology (ISGEO). Unlike the previously used system that was symptom-based, the ISGEO system describes the natural history, staging, tissue damage affecting visual function, and mechanisms for angle-closure. Dr Thygesen encouraged clinicians to follow the European Glaucoma Society guidelines flowchart for treatment, and he reviewed the indications, effectiveness and drawbacks of the various surgical treatment options for PAC/PACG. The list includes laser peripheral iridotomy, argon laser peripheral iridoplasty, anterior chamber paracentesis, goniosynechialysis, trabeculectomy, and lens extraction. He noted lens extraction is currently a hot topic with the reporting of results from the EAGLE study. EAGLE enrolled patients with PACG with intraocular pressure (IOP) >21mmHg or PAC with IOP ≥30mmHg. Other eligibility criteria required angle-closure, either appositional or synechial in 180 degrees or more, phakic status with absence of cataract, age 50 years or older, and diagnosis within six months. EAGLE found that initial treatment with lens extraction was more effective and cost-effective than laser iridotomy with medical therapy. Based on the outcomes, the investigators concluded that lens extraction should be considered as an alternative to current practice. However, they also observed that there is an increased risk of posterior capsule rupture when performing lens extraction in eyes with angle-closure and that the results of EAGLE are not applicable to other types of PACs/PACGs. Dr Thygesen noted that EAGLE had other limitations, including that the participants were not masked, a large proportion of gonioscopic data were not reported, and definitions of complications were not standardised. In addition, he cautioned that one good quality trial may not be enough to change policy. “For sure we should still be doing primary iridotomy. Cataract surgery alone may be considered in some mild cases, and the results of the EAGLE study say the same. However, we do not need to do lens extraction in all cases,” Dr Thygessen said.