A study was designed to validate a functional investigation performed with the scanning laser ophthalmoscope before surgery for macular holes in 12 eyes: The assessment included fundus examination, a functional examination resulting in evaluation of the preferred retinal lows, visual acuity and recording of visual evoked potentials. The preferred retinal locus was evaluated by presenting a small square area, and visual acuity was determined by means of calibrated figures. The visual evoked potentials were evoked by three alternating checkerboards (check size, 30', 2 Hz) centered over the hole and seen at an angle of 6.5 x 6.5 degrees, 2.5 x 2.5 degrees and 6.5 x 6.5 degrees with central exclusion of 2.5 x 2.5 degrees. The appearance of the fundus visualized by scanning laser ophthalmoscopy consisted of a clear central disk corresponding to the hole, surrounded by a very dark ring, associated with a second, less dark ring with unclear margins. Fixation was unstable in one case with a visual acuity of 20/70. In 11 cases, fixation was localized to the superior retina with a visual acuity superior to 20/70. The visual evoked potentials evoked by 6.5 x 6.5 degrees were discernible in all 12 eyes; visual evoked potential by annular stimuli were discernible in 11 cases. The 2.5 x 2.5 degrees stimulus evoked no response in eight cases, proving the area of the hole was nonfunctional. A response was recorded in the four other cases, where the dimension of the holes was less than 2 degrees. The results of this scanning laser ophthalmoscopic assessment demonstrated a precise evaluation of the residual macular function in the cases of full-thickness macular holes.