Argon green vs. krypton red laser photocoagulation for extrafoveal choroidal neovascularization secondary to age-related macular degeneration: 3-year results of a multicentre randomized trial. Canadian Ophthalmology Study Group.
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OBJECTIVE: To determine whether argon green laser (AGL) or krypton red laser (KRL) is superior for the treatment of well-defined extrafoveal choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD) after 3 years of follow-up. DESIGN: Multicentre randomized clinical trial. SETTING: University-based referral practices in Canada. PARTICIPANTS: Among 210 patients selected by ophthalmologists at 13 participating centres there were 191 eligible patients aged 50 years or more with angiographically proven CNV whose posterior edge was 200 to 2500 microns from the foveal avascular zone. Other inclusion criteria included the presence of drusen in either eye, a best corrected visual acuity in the study eye of at least 35 letters on the Early Treatment Diabetic Retinopathy Study chart (equivalent of 20/200 or better on the Snellen chart) and no prior photocoagulation in the study eye. The patients were randomly assigned to receive either AGL (96 patients) or KRL (95 patients) treatment. INTERVENTIONS: Treatment with 200-microns spots of 0.2 to 0.5 seconds' exposure to produce a homogeneous grey white lesion that completely covered the CNV. OUTCOME MEASURES: Change from baseline in visual acuity at 1, 2 and 3 years (primary measure), development of persistent or recurrent CNV (secondary measure). RESULTS: There were no significant differences between the treatment groups in drop-out rates. No significant differences were found between the two groups in loss of visual acuity or angiographic evidence of persistent or recurrent CNV. CONCLUSION: KRL is no better than AGL in preserving vision and preventing loss of visual acuity in patients with AMD with well-defined extrafoveal CNV followed for 3 years.
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