Prolonged activity of retinal ganglion cells following intense, nanosecond laser flashes

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Abstract

1. The effects of intense, but nonlesion producing, laser exposures of 20-ns duration were determined on the light responses and spontaneous activity of retinal ganglion cells recorded in situ from the rhesus monkey. 2. Following a single, 20-ns exposure centered on its receptive field, a ganglion cell produced an 'afterdischarge' of maintained action potentials. 3. The duration of the afterdischarge depended on the diameter of the laser beam on the retina and on the beam's intensity. 4. Laser exposures subtending 0.5 or 2.0 deg, and delivering 45 to 60% of the maximum permissible exposure, elicited afterdischarges which lasted up to 80 s. When the laser beam diameter was decreased to 0.25 deg, the afterdischarge was reduced to 30 s, and to less than 5 s with a 0.12-deg laser beam. 5. Light sensitivity after the laser exposure recovered rapidly during the first 10 s and then more slowly, but exponentially, until it reached the preflash level. The time constant of recovery after the 0.5- and 2.0-deg exposures was 35 and 9 s after the 0.25-deg exposure. The time course of threshold recovery was similar, but not identical to the duration of the afterdischarge. 6. Color-opponent ganglion cells exhibited a phenomenon called 'response reversal' after the laser exposure, presumably due to selective adaptation of a mid-wavelength cone input. 7. The afterdischarge appears to be a physiological correlate of the 'dark light' signal presumed to account for bleaching adaptation. Afterdischarges do not appear to be involved in field adaptation. 8. A 20-ns exposure, regardless of intensity, is unlikely because of photoregeneration to bleach more than half of the available visual pigment. Therefore, the effects on ganglion cell response described here are not likely to be due solely to pigment bleaching.

Original languageEnglish (US)
Pages (from-to)1-18
Number of pages18
JournalClinical Vision Sciences
Volume4
Issue number1
StatePublished - Jan 1 1989

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ASJC Scopus subject areas

  • Ophthalmology

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