DOES THE BORDER OF A BLIND SPOT (AS DETER MINED BY FUNDUS PERIMETRY) DEPEND ON THE SURFACE-TOPOGRAPHY OF THE PAPILLA

Background: We wanted to find out whether the borders of the blind spo t depend on the surface topography of the optic disc and its surroundi ng area. Patients and methods: We therefore examined ten eyes with par apapillary atrophy adjacent to the temporal side of the disc. Fundus p erimetry was performed under direct fundus control using a Rodenstock scanning laser ophthalmoscope. We examined the horizontal meridian of the optic discs in 0.5 degrees steps using Goldmann IV-stimuli with 10 different degrees of brightness and the Gold mann stimulus I, 0 dB (g reatest luminance). Six eyes with symmetric, ''normal'' excavation ser ved as controls. Optic disc topography was measured with the Heidelber g Retina Tomograph (HRT). Results: Stimuli with a large luminance powe r (Goldmann IV, 4 dB) were seen up to 0.8 degrees centrally (i.e., tow ards the optic disc center) from the temporal edge of the parapapillar y atrophy, but up to 1.9 degrees centrally from the nasal optic disc b order (P<0.01). Horizontal HRT section profiles of the optic disc cons istently showed prominent nasal disc borders contrasting with a shallo w excavation within the temporal parapapillary atrophy. ln all six sub jects with a normally shaped disc there was no such ''nasotemporal asy mmetry.'' Conclusions: The size of scotomas depends on the surface top ography of the tested area. The prominent nasal part of the optic disc appears less ''blind'' than the shallow temporal part, probably due t o more intensive light scattering by the prominent nasal part of the d isc.