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Editors Selection IGR 7-3

Surgical treatment: Iridectomy in ACG

Comment by Paul Foster on:

12472 Cataract progression after prophylactic laser peripheral iridotomy: potential implications for the prevention of glaucoma blindness, Lim LS; Husain R; Gazzard G et al., Ophthalmology, 2005; 112: 1355-1359

Find related abstracts

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Lim et al. (666) report progression of lens opacities in 60 Singaporean patients with unilateral symptomatic angle-closure undergoing prophylactic laser iridotomy in their 'unaffected' fellow eyes. Lens opacities were graded through a dilated pupil by different observers using the LOCS III reference images at 2 weeks, 4 months and 12 months after laser PI. The proportions of people with progression (change of 2 or more LOCS units) in lens opacity in this study are 5% nuclear sclerosis, 6.7% cortical and 16.7% PSCC. The authors compare these with figures of incident lens opacity from population-based research. The data for NSC and cortical change should be regarded as inconclusive, however it does appear that the subjects in this study did have a higher rate of PSC progression than reported in population-based studies of incidence.

Peripheral iridotomy may cause posterior subcapsular lens opacities

Several possible sources of bias exist. Ninety subjects were recruited, but 5 underwent cataract surgery during the study suggesting that they had significant cataract at enrolment. A further 25 were lost to follow-up, probably indicating that most had no significant concerns about their vision during the follow-up period. The omission of data on the 33% of enrolled subjects from the analysis may well have inflated the apparent size of any possible adverse effect. While the observers who performed the lens grading were masked to the results of the previous examinations, they were aware that a laser iridotomy had been performed, and were not masked to the hypothesis being tested. Furthermore an assessment of inter-observer agreement was not performed. Consequently bias, attributable to different observers or failure to standardize slitlamp illumination settings, remains a possibility. It would be ethically difficult to enroll a control group, however, this would be scientifically desirable. The lack of a comparative control group weakens the study. However, the key issue with this study is that it addresses progression, and not incidence. Until incidence of PSCC is studied, the findings will remain inconclusive. The study is thought-provoking and does require independent verification. However, it does highlight important questions about the safety of laser PI on a large scale for prevention of angle-closure glaucoma.