Laser photocoagulation for choroidal neovascularisation in pathologic myopia

Abstract

Background: Pathologic myopia is usually defined as the need for a spectacle correction of -6 diopters or higher. Choroidal neovascularisation (CNV) is the most commonly occurring cause of visual loss in people with pathologic myopia. In myopic macular degeneration the occurrence of newly formed vessels in the macula often leads to a fibrotic pigmented scar causing a blind spot in the centre of the visual field.

Objectives: The primary objective of this review was to examine the effects of laser photocoagulation for CNV associated with pathologic myopia. A secondary objective was to compare the effects of different photocoagulation techniques.

Search strategy: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) on The Cochrane Library (Issue 2, 2005), MEDLINE (1966 to July 2005), EMBASE (1980 to July 2005, week 28), LILACS (July 2005) and the reference lists of included studies.

Selection criteria: We included randomised controlled trials comparing photocoagulation with observation or comparing different photocoagulation techniques in people with CNV associated with myopia of -6 diopters or higher.

Data collection and analysis: Two authors independently assessed the search results for eligibility.

Main results: Two studies were included that enrolled people with CNV located at 100 microns or more from the foveal centre. One study compared photocoagulation with observation. At the final examination, 16/35 participants randomised to photocoagulation versus 31/35 randomised to observation had visual acuity of 20/100 or worse after 6 to 48 months. The second study randomised 27 eyes (26 patients) to photocoagulation with three laser wavelengths (9 eyes per group). The number of eyes losing two or more lines was 2 (577 nm), 3 (590 nm) and 3 (620 nm) after 3 to 17 months. In both studies comparisons were made using outcomes assessed at the final examination. As the final examination took place at different follow-up times it was difficult to interpret the findings and it was impossible to extract data for further analyses.

Authors' conclusions: Despite its use over several years the effectiveness of laser photocoagulation for myopic CNV has not been established. Although there was a suggestion of short-term effectiveness in one small study on non-subfoveal CNV the results were potentially biased. Observational studies suggest that the enlargement of the atrophic laser scar after laser treatment of non-subfoveal CNV could be a potentially vision-threatening long-term complication, even in eyes free of CNV recurrence.