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Editors Selection IGR 18-2
Comment
Comment by Benjamin Xu on:
70327 Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomised controlled trial, Azuara-Blanco A; Burr J; Ramsay C et al., Lancet, 2016; 388: 1389-1397
See also comment(s) by Rupert Bourne • Clement Tham • Jennifer Burr & Augusto Azuara Blanco •The Effectiveness of Early Lens Extraction for the Treatment of Primary Angle-Closure Glaucoma (EAGLE) study is a well-designed and thought-provoking randomized control trial. It compares clear lens extraction to laser peripheral iridotomy (LPI) in the management of patients with primary angle closure (PAC) and primary angle-closure glaucoma (PACG). Its results describe the benefits of clear lens extraction and LPI in terms of intraocular pressure (IOP) lowering, patient-reported quality of life metrics, and long-term cost effectiveness.
The management of angle-closure patients presents a clinical challenge for glaucoma specialists. The standard of care for PACG patients with clear lenses is to perform an LPI followed by trabeculectomy or glaucoma drainage device surgery if IOP remains uncontrolled with topical medications. Recent work has demonstrated that the lens plays a key role in the pathogenesis of angle closure.1 In light of these developments, one study compared the effectiveness of clear lens extraction versus trabeculectomy in PACG patients.2 Its results suggest that cataract surgery alone is an effective means of controlling IOP even in the absence of a visually significant cataract.
The EAGLE study takes this discussion one step further and makes the argument that clear lens extraction should be the first-line treatment in the management of PACG patients. I have two major concerns with the broad applicability of this approach: adverse events and unhappy patients. The authors anticipated these concerns and use the data to argue that clear lens extraction is associated with a low rate of adverse events and high degree of patient satisfaction. However, given the modest difference in IOP reduction between the two treatment groups, it is debatable if the benefit outweighs the risks, even when the rate of serious complications is low. The authors speculate that surgical patient satisfaction may be due in part to an improvement in visual function. This brings into question the study's definition of a clear lens, which intuitively should not contribute to any visual impairment. Was it simply 20/20 best corrected visual acuity? Were assessments such as glare testing performed? The distribution of refractive errors in the study population is also not made clear, including the percentage of hyperopic patients. When compared to hyperopes, emmetropes and myopes with excellent visual acuity are more likely be unhappy with a sub-optimal refractive outcome and full-time spectacle dependence.
Recent debates have questioned the role of LPI in the management of angle-closure patients. While the utility of LPI in angle closure suspects is still under investigation, the EAGLE study presents compelling evidence for performing LPIs in patients who have manifested elevated IOP or glaucoma. The authors briefly discuss the IOP-lowering benefit of clear lens extraction over LPI, but do not conjecture as to why this advantage is so modest. This result is puzzling given the large difference in anatomical changes induced by the two treatment modalities.3 The data also does not explicitly mention the number of surgical patients who received goniosynechiolysis, which by itself is a potent IOP-lowering treatment in angle closure patients.4 The fact that the majority (89%) of LPI patients did not require surgical intervention during the threeyear follow-up further supports the effectiveness of LPIs.
The authors should be commended on providing practitioners with robust evidence to guide the management of a challenging disease entity. My interpretation of the EAGLE study is that clear lens extraction is a viable alternative to LPI, especially in patients who may derive a refractive benefit or have difficulty tolerating topical medications. However, the lack of dramatic benefit in terms of IOP reduction is disappointing, especially considering the potential pitfalls associated with performing surgery on patients with excellent vision. Given the efficacy, safety profile, and facility of performing an LPI, this study makes a strong case for LPI as a viable first-line treatment for the majority of angle-closure patients.
References
- Nongpiur ME, et al. Lens Vault, Thickness, and Position in Chinese Subjects with Angle Closure. Ophthalmology 2011;118:474-479.
- Tham CCY, et al. Phacoemulsification versus Trabeculectomy in Medically Uncontrolled Chronic Angle-Closure Glaucoma without Cataract. Ophthalmology 2013;120:62-67.
- Melese E, et al. Comparing Laser Peripheral Iridotomy to Cataract Extraction in Narrow Angle Eyes Using Anterior Segment Optical Coherence Tomography. PLoS One 2016;11, e0162283.
- Qing G, Wang N, Mu D. Efficacy of goniosynechialysis for advanced chronic angle-closure glaucoma. Clin Ophthalmol 2012;6:1723-1729.
