Macular sparing as a perimetric artifact.

Abstract

We studied the hypothesis that the typical macular sparing of a few degrees was based on an unstable fixation coupled with a nystagmiform searching movement in the direction of the seeing hemiretina. By means of microperimetry with a scanning laser ophthalmoscope, we recently tested the visual fields of 15 hemianoptic patients, through direct visual control of the retina. The tests provided us with accurate information about all fixation shifts that occurred. Twelve patients showed macular sparing of 1 to 5 degrees both in the Goldmann visual field and in the scanning laser ophthalmoscope field. Their fixation shifted regularly 1 to 10 degrees toward the seeing hemiretina one to two times per second, then returned rapidly to the foveola. Conversely, three patients showed greater macular sparing, and they all had particular characteristics--extensive fixation shifts, dual fixation, and limited quadrantanopsia. We believe that macular sparing could be interpreted as a perimetric (not an anatomic) artifact, provided that the results of these tests on 15 patients are confirmed by further similar studies.