Evidence mounts for lens extraction as angle closure treatment

Over the past eight years, significant evidence has emerged supporting lens extraction as an effective treatment for primary angle closure and angle closure glaucoma, Nicholas P Bell MD of the University of Texas told Glaucoma Day 2014 at the American Society of Cataract and Refractive Surgery annual meeting in Boston.

Dr Bell noted that much has changed since a 2006 Cochrane review concluded that no good evidence existed for lens extraction in treating angle closure (Cochrane Database Review 2006 Issue 3). He cited a 2008 Hong Kong study that found lens extraction with IOL implant superior to laser or surgical peripheral iridotomy in controlling intraocular pressure and reducing the number of medications required to control IOP, with differences increasing over time out to 18 months (Lam Ophthalmology 2008).

A 2008 Japan study reported similar results (Hata J Med Invest 2008) while a 2012 Singapore study found phaco with IOL much more successful than LPI in preventing progression to filtration surgery in cases of acute PAC at two years (Husain et al Ophthalmol 2012). Two studies from Hong Kong also found LE equivalent to trabeculectomy in controlling IOP (Tham et al. Opthalmol 2008 and Opthalmol 2013). These contributed to a 2014 Cochrane review concluding that LE may be more effective than laser or incisional glaucoma procedures (Emanuel et al Curr Opin Ophthalmol 2014, 25:89-92).

If a visually significant cataract is present, Dr Bell recommends LE for treating cases of suspected primary angle closure, primary angle closure and primary angle closure with glaucoma. Without a cataract, he still recommends LE for PAC with glaucoma, but an LPI for PAC suspects and “a long discussion with the patient” for making the decision in cases of PAC.

Avoiding lawsuits after iridotomies

Linear dysphotopsias and missed narrow angles are two of the most common – and two of the most potentially disabling – adverse outcomes after peripheral iridotomy, Devesh K Varma of the University of Toronto told Glaucoma Day 2014 at the ASCRS annual meeting in Boston. Steps can be taken to avoid both, improving patient outcomes and reducing the risk of being sued, he added.

Linear dysphotopsias, or the appearance of a bright line across the bottom of the visual field, are more common and more difficult to treat than most iridotomy complications, Dr Varma noted. Location seems to play a big role.

Research conducted at the University of Toronto found that among superior iridotomies, 10.7 per cent resulted in linear dysphotopsias compared with just 2.4 percent of temporal iridotomies. Further, in most cases of superior iridotomies resulting in linear dysphotopsias, the eyelid partially covered the iridotomy. Dr Varma and colleagues hypothesize that superior iridotomies interact with the tear meniscus along the upper eye lid to reflect light a short distance onto the superior retina, creating a relatively focused image. The longer path light travels from a temporal iridotomy scatters more, reducing the intensity of any dysphotopsia.

By comparison, the risk of IOP spikes after iridotomy is 0.5 per cent or less, about 10 per cent for uveitis lasting more than one week and 34.6 per cent for bleeding, all of which are temporary and relatively easily managed. Serious complications are much less frequent with retinal detachments at 0.3 per cent and long-term PI closure at 2.0 per cent. The impact of iridotomy on the risk of cataracts and endothelial loss is unclear but apparently rare, Dr Varma said.

Unresolved narrow angles and missed angle closure after PI fall into the category of diagnosis failures, which are responsible for about 33 per cent of lawsuits against ophthalmologists in the US, compared with 23 per cent resulting from complications, Dr Varma said. They are also very common.

Examining referrals to his clinic, Dr Varma found that 10.1 per cent of 976 cataract referrals had narrow or closed angles for 180 degrees or more. More surprising, out of 1,234 glaucoma referrals from ophthalmologists, only 179 included angle status and 8.9 per cent had missed angle closure glaucoma. Other studies report that 16 per cent to 38 per cent of angles remain narrow after LPI, of which 28 per cent progress to primary angle closure glaucoma, which is responsible for half of all glaucoma blindness.

Dr Varma attributes these oversights to ophthalmologists either not looking for angle closure, or not detecting it due to improper technique. Angles that close completely with no light often are missed because they remain open if ultrasound or OCT are conducted with too much ambient light. He emphasized the importance of minimizing light and allowing patients to adapt to low light before running tests.