[Experimental studies of locally generated focal VECP within the 30 degree visual field with LED]

Measuring and evaluating locally generated VECP present a chance to overcome methodical restriction in conventional subjective perimetry. To achieve this, stimuli are required which ensure the generation of detectable responses under controlled scattered light influence. The suitability of LED for this task was studied. LED stimuli (lambda = 560 nm) were moved in steps of 3 degrees from 0 degree to 30 degrees on the horizontal meridian within a perimeter sphere. The stimuli were 0.8 degree and 1.7 degrees in size, 20 ms in duration and 0.5 Hz in frequency. The background illumination was 10 cd/m2. A total 467 responses recorded from 20 volunteers (age 26 +/- 2) known to be free of any visual field defect have been evaluated. Using only one LED (size 0.8 degree) VECPs are detectable in the visual field < 9 degrees exclusively. An increase of stimuli size to 1.7 degrees made the generation of detectable VECP within the peripheral visual field possible. Statistical evaluation (sign test) proved significantly that VECP can be reliably elicited under LED stimulation. LED (lambda = 560 nm) are suitable for the generation of localized VECP in the visual field up to an eccentricity of 30 degrees.