Fixation and central visual field after perifoveal krypton laser treatment of subfoveal neovascularizations.

In contrast to focal laser treatment of large subfoveal neovascular membranes, perifoveal laser treatment sparing the central avascular zone can partially retain central macular function in some cases. The anatomical and functional outcome of this technique was analysed in 26 patients with large subfoveal neovascular membranes (0.6 to 3.0 disc diameter) secondary to age-related macular degeneration (24 cases) or presumed ocular histoplasmosis syndrome (two cases). Patients were followed for six to 39 months. Out of 26 patients 21 had a stable dry scar at the last follow-up examination. Central fixation was retained postoperatively in nine out of 13 patients with central fixation prior to laser treatment. Visual acuity was maintained or improved in 19 out of 26 treated eyes. Statpack analysis (Humphrey Field Analyser) of the long-term results of patients with central fixation indicated an increase in the depth of their relative central scotoma not only immediately after laser treatment but also in the first and second postoperative years. This increasing depth of central scotoma subsequently led to a shift of central fixation to a paracentral area in four out of nine patients six to nine months after treatment. Indocyanine-green angiography showed remaining subfoveal choroidal vasculature corresponding to the area of central fixation, as found in fundus microperimetry by scanning laser ophthalmoscope. Perifoveal laser treatment seems to be effective in maintaining some initial macular function for a limited time in selected patients suffering from subfoveal neovascular membranes.