EAGLE is an international multicentre pragmatic randomised controlled trial

EAGLE is an international multicentre pragmatic randomised controlled trial (RCT) designed to establish whether lens extraction for newly diagnosed primary angle-closure glaucoma (PACG) results in better patient-reported health, vision, lower intraocular pressure (IOP) and other outcomes compared with standard management. The World Health Organization ranks glaucoma as the second most common cause of blindness after cataract, and as the leading cause of irreversible blindness. There are two types of glaucoma: open-angle and angle-closure. Although primary open-angle glaucoma (POAG) is the more common, PACG is the more severe (more likely to result in irreversible blindness if not properly treated). By 2020, PACG will affect 20 million people, and 5.3 million will be blind. In the UK, PACG affects between 50,000 and 100,000 people, and is estimated to cause 1,000 people to suffer irreversible blindness every year, and many more live with the disability and reduced quality-of-life associated with glaucoma. PACG is more common in East Asia than the rest of the world. Older age and female gender are demographic risk factors. Having a small eye and thus hypermetropia is also an important risk factor. The number of people diagnosed with PACG is predicted to increase substantially over the next few years as the result of an ageing population. The current standard care for PACG is a stepped approach of a combination of surgery (laser or incisional) and medical management. Initial surgery uses a laser to make a small hole in the iris (laser iridotomy/LI) to open the drainage angle, and often eye drops are required as an adjunct to LI to further reduce the IOP. There are several types of drops used to lower IOP, but prostaglandin and beta-blocker treatments are the most commonly used. If these first line treatments fail, glaucoma surgery (e.g. trabeculectomy) is then indicated. Trabeculectomy may fail to control the IOP, and in PACG complications (such as flat anterior chamber and malignant glaucoma) are more likely than for other types of glaucoma. These standard approaches to PACG management have been noted to have variable success. A new approach to the management of patients with PACG (lens extraction by phacoemulsification) has gained recent interest among specialists internationally. Because the lens of the eye plays a major role in the mechanisms leading to PACG, including pupillary block and angle crowding, the hypothesis is that PACG could be treated by removing the lens (by phacoemulsification). For glaucoma patients with cataract, lens extraction is always required. However, in the absence of cataract, whether to extract the lens, and the timing of such intervention, remains open to debate.

EARLY EXTRACTION

It is likely that many people with PACG will go on to develop cataracts and require surgery due to ageing and the effect of conventional glaucoma treatment, which may accelerate cataract progression - but by this stage irreversible glaucoma damage and sight loss may have occurred. It is proposed that early clear lens extraction will improve glaucoma control by opening the drainage angle. This should reduce the need for medications and trabeculectomy, maintain good visual acuity, and improve quality-of-life compared with standard care. It will also improve the visual function in patients with hypermetropia (found in the majority of PACG patients), by correcting this refractive error. The hypothesis tested in the EAGLE trial was that those randomised to early lens extraction would have a higher EQ-5D score, lower IOP, and lower trabeculectomy rate than those randomised to standard care at three years. Recruitment took place in centres in the UK, East Asia and Australia. Patients were newly diagnosed with either: 1) PACG; or 2) primary angle-closure (PAC) and with IOP>30mmHg at diagnosis. They were phakic in the affected eye and 50 years or older.

COMPLICATION RISKS

Patients were excluded if they had advanced glaucoma, i.e. visual field loss (mean deviation worse than -15dB), or cup-disc-ratio >0.9; previous attack of angle closure; increased surgical risk: e.g. corneal opacity, Fuch’s endothelial dystrophy; pseudoexfoliation; previous vitreoretinal surgery; not able to be positioned to undergo standard technique; symptomatic cataract in either eye; previous LI; axial length A total of 419 participants were randomised in equal proportion to lens extraction or LI and followed for three years. Surgeons involved in the study were all experienced in glaucoma and cataract surgery. The results of the EAGLE trial will be published in the near future in The Lancet, but we provide a brief summary of the results that were presented at the recent 12th European Glaucoma Society Congress. In brief, the group of participants who underwent lens extraction had better quality-of-life compared with those who underwent LI, and this was also associated with better glaucoma control (lower IOP, less number of medications and less glaucoma surgery). However, there is a risk of complications, particularly posterior capsule rupture, which was observed in about one per cent of participants undergoing lens extraction. The possibility of surgical complications in people with clear lens and good vision warrants an individualised approach and careful discussion of risks and benefits. The results of the EAGLE study are not generalizable to other people with e.g. narrow angles or primary angle-closure suspects. EAGLE was funded by MRC and managed by NIHR on behalf of the MRC-NIHR Partnership. The views expressed in this publication are those of the author and not necessarily those of the MRC, NHS, NIHR or the Department of Health * Augusto Azuara-Blanco PhD, FRCS(Ed), FRCOphth is Professor of Ophthalmology, Queen's University Belfast, Northern Ireland, and Honorary NHS Consultant Ophthalmologist, BHSCT Institute of Clinical Sciences, Belfast. He can be reached at: a.azuara-blanco@qub.ac.uk

Tags: lens extraction, primary angle-closure glaucoma