Relationship of nerve fiber layer defects and parafoveal visual field defects in glaucomatous eyes

To evaluate the relationship between nerve fiber layer defects (NFLD) and parafoveal visual field defects in glaucomatous eyes, 23 eyes of 20 patients with open-angle glaucoma were studied by scanning laser ophthalmoscope (SLO). Only eyes in which the NFLD reached the temporal raphe in either hemisphere were used. We defined three topographic parameters of NFLD: 1) the angle (theta, degrees) of line 'A' from the optic disc center to the foveal pit, and line 'B' from the disc center to a point of the NFLD at the disc edge nearest line 'A'; 2) a horizontal distance (D1, mm) along the temporal raphe between the foveal pit and the internal edge of the NFLD; and 3) a vertical distance (D2, mm) between the foveal pit and either the superior or inferior internal edge of the NFLD. We defined the nearest defect location (in degrees from the fovea) as the nearest location with sensitivity loss of at least 6 dB (Humphrey visual field program 10-2). A highly significant correlation was found between each of the NFLD parameters and the nearest defect location (P < 0.001). The NFLD parameters we defined may be helpful for evaluating parafoveal visual function in glaucoma.