Pattern reversal ERG with LED-stimulation using cyclic summation technique.

PURPOSE

Multifocal pattern reversal stimulation can be used to detect inner retinal dysfunction. Commonly, the stimulus is generated on a monitor using m-sequence technique. We describe a pattern reversal ERG evoked by LED arrays using cyclic summation (CS).

METHODS

One eye of eight healthy subjects was examined with an arrangement of 13 LED arrays. Each array consisted of 100 LEDs separated by thin walls. One of the fields was placed centrally, three fields each were placed above, below, left and right of the central field. CS technique at a temporal frequency of 16 reversals per second (RPS) was used for stimulation. Viewing distance was 30 cm, check size was 0.58 cyc/deg. Luminance of the bright fields was 340 cd/m2.

RESULTS

Fourier analysis was performed. Centrally, the amplitude of the 2nd harmonic wave was highest (0.87 microV). In the first paracentral fields, amplitudes were 0.28 microV (nasally), 0.21 microV (superior, inferior and temporally). In the second paracentral fields, amplitudes were 0.11 microV (nasally), 0.09 microV (superior), 0.13 microV (inferior) and 0.15 microV (temporally). With exception of the temporal field (0.1 microV), in the outermost fields no reproducible ERG response could be recorded.

CONCLUSION

Peripheral ERG responses to a pattern reversal stimulus can be recorded with LED stimulation using CS technique up to an eccentricity of 30 degrees. Responses are highest centrally and decrease with increasing distance to the centre.