| Abstract: | BACKGROUND: We wanted to find out whether the borders of the blind spot depend on the surface topography of the optic disc and its surrounding area. PATIENTS AND METHODS: We therefore examined ten eyes with parapapillary atrophy adjacent to the temporal side of the disc. Fundus perimetry was performed under direct fundus control using a Rodenstock scanning laser ophthalmoscope. We examined the horizontal meridian of the optic discs in 0.5 degree steps using Goldmann IV-stimuli with 10 different degrees of brightness and the Goldmann stimulus 1, 0 dB (greatest luminance). Six eyes with symmetric, "normal" excavation served as controls. Optic disc topography was measured with the Heidelberg Retina Tomograph (HRT). RESULTS: Stimuli with a large luminance power (Goldmann IV, 4 dB) were seen up to 0.8 degree centrally (i.e., towards the optic disc center) from the temporal edge of the parapapillary atrophy, but up to 1.9 degrees centrally from the nasal optic disc border (P < 0.01). Horizontal HRT section profiles of the optic disc consistently showed prominent nasal disc borders contrasting with a shallow excavation within the temporal parapapillary atrophy. In all six subjects with a normally shaped disc there was no such "nasotemporal asymmetry." CONCLUSIONS: The size of scotomas depends on the surface topography of the tested area. The prominent nasal part of the optic disc appears less "blind" than the shallow temporal part, probably due to more intensive light scattering by the prominent nasal part of the disc. |
