Argon green vs krypton red laser photocoagulation for extrafoveal choroidal neovascularization. One-year results in ocular histoplasmosis. The Canadian Ophthalmology Study Group

OBJECTIVE: To determine whether the krypton red laser is superior to the argon green laser or vice versa for treatment of choroidal neovascularization located between 200 and 2500 microns from the center of the foveal avascular zone in patients with ocular histoplasmosis syndrome. DESIGN: Multicenter, randomized, controlled clinical trial. SETTING: Ophthalmologic clinics throughout Canada. PARTICIPANTS: Patients who provided informed consent, were aged 18 years or older, and had extrafoveal membranes associated with ocular histoplasmosis syndrome. RESULTS: One hundred forty-one patients were randomized, 134 (95%) of whom were determined eligible. Of the eligible patients, 128 (96%) had sufficient follow-up for the primary outcome comparison of visual acuity at 1 year. In the argon green laser group, there was a mean increase of 3 letters at 1 year, while in the krypton red laser group there was a mean decrease of 2.5 letters in visual acuity. CONCLUSION: The krypton red laser is no better than the argon green laser for the treatment of well-defined extrafoveal choroidal neovascularization secondary to ocular histoplasmosis syndrome.