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S. Bültmann, P. Weimer, K. Rohrschneider; The Blind Spot Signal in Scanning Laser Ophthalmoscope Multifocal ERG . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4195.
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Purpose: To investigate the occurrence of a blind spot signal in multifocal ERG under direct fundus visualization. Methods: 8 eyes of 8 normal subjects were examined with the RETIscan (Roland Consult, Germany) using the Scanning Laser Ophthalmoscope (SLO, Rodenstock) following pupil dilation at 235 cd/m2 stimulus intensity with 92% contrast. We used gold-foil electrodes and an evenly distributed 19-hexagon pattern with eccentric fixation target so that one hexagon would exactly cover the disc. Eight 45-second recordings were averaged per eye and fixation stability monitored by video recording. We evaluated P1 amplitude and implicit times of the first order kernel. Results: Stable central fixation was maintained in all eyes. A blind spot signal could be observed in 5 eyes, while no signal was found in 3. The blind spot signals appeared to be configured regularly without considerable shift in implicit times. The P1 amplitude was reduced. Conclusion: In monitor mfERG stimulation the blind spot signal may be valuable in judging fixation stability. However, it is not frequently recorded even when normal subjects with stable fixation are considered. Hexagon-misplacement and light-scattering by the optic media or the disc are frequently discussed as a reason. During fundus perimetry with the SLO light scattering or reflection at prominent tissue on the fundus has been shown to be of minor importance in the region of the optic nerve head. Therefore other reasons for signals at the disc must be considered.
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