High myopia and choroidal neovascularization: microperimetry guided selection for photocoagulation

Purpose. To demonstrate that a precise identification of the center of fixation in patients with high myopia and choroidal neovascularization (CNV) can lead to a better selection of those eyes eligible for photocoagulation. Methods. Sixty-one eyes of 59 patients with high myopia and CNV were submitted to a fluorescein and indocyanine green angiography in order to identify the neovascular membrane and the foveal avascular zone (FAZ). The patients were also examined by fundus pe- rimetry using a scanning laser ophthalmoscope (SLO) to obtain an objective documentation of the center of fixation The angiography and the fundus perimetry with the fixation area were then aligned and superimposed. The relative distances among CNV, FAZ and the center of fixation were eventually calculated. Results. The distance between the CNV boundaries and the center of fixation was less than 200 µ in 45 eyes (74%), while in the remaining 16 eyes ranged between 200 µ and 750 µ (mean 380 µ). The center of fixation was within the FAZ in 38 eyes (62%), while in 23 eyes (38%) it could be identified out the edge of the FAZ at a mean distance of 320 µ. Conclusions. Due to the heavy changes of the posterior retina in high myopia, the conventional techniques of identification of the fixation area do not lead to satisfactory results. The fundus perimetry with the SLO demonstrates that in more than one-third of these patients the anatomic fovea and the functional fovea do not correspond. Furthermore, most cases of CNV lay at a short distance from the center of fixation which means that laser photocoagulation of the choroi- dal membrane could dramatically affect the visual acuity. None.,.....