Absolute sensitivity of the electroretinogram and of the optic nerve action potential in the perfused feline eye.

Purpose: To assess and characterize the electroretinogram (ERG) and the optic nerve response (ONR) at threshold stimulus intensity in the isolated perfused cat eye.

Methods: Eyes were enucleated from deeply anesthetized adult cats and arterially perfused with oxygenated serum-enriched tissue culture medium. Light stimuli of 20- to 400- msec duration from a xenon arc source, attenuated down to threshold intensities by neutral density filters, were delivered via a modified fundus camera in full dark adaptation. Vitreal ERGs and ONRs were amplified, digitized, averaged and analyzed using LabVIEW for Windows software.

Results: The threshold intensities in log scot q/deg(2) per second for the negative scotopic threshold response (STR), for the ERG b-wave, and for the ONR were at 2.87+/-0.35, 3.53+/-0.35 and 1.78+/-0.48, respectively.

Conclusion: The in vitro perfused mammalian eye preparation exhibits remarkably low thresholds for the ERG and particularly for the ONR near the intensity required for the human psychophysical threshold.