Prophylactic argon laser photocoagulation of the second eye in presumed ocular histoplasmosis syndrome.

Fifty-six patients with presumed ocular histoplasmosis syndrome who exhibited a disciform macular detachment or macular scar in one fundus and one or more inactive atrophic lesions within the high-risk area of the second eye were seen at the Retina Service of Maisonneuve-Rosemont Hospital, Montreal, between 1972 and 1984. All 56 were followed for at least 10 months. Of the 56, 28 had received prophylactic argon laser photocoagulation of the inactive chorioretinal lesions. The rate of activation of the lesions was similar in the treated and untreated groups (10/28 over a mean follow-up period of 44.2 months and 11/28 over a mean period of 43.2 months respectively). In the untreated group there was an increased risk of activation with a higher number of lesions (t = 2.386). In both groups the risk of activation increased with the proximity of the lesions to the centre of the fovea (chi 2 = 29.97). Of the 10 treated eyes that showed activation, 4 did so within 1 month, which suggests that prophylactic photocoagulation may not be without risk of complications.