Influence of anesthetics, ethyl alcohol, and Freon on dark adaptation of monkey cone ERG

Cone dark adaptation curves were measured in a rhesus monkey using the electroretinogram (ERG) response to a 40 Hz flickering stimulus. The influence of anesthetics on the time course of dark adaptation was studied. All volatile anesthetics tested (methoxyflurane, halothane, enflurane, ether, chloroform) retarded dark adaptation but to different degrees; urethane, ethyl alcohol, and Freon 11 also retarded dark adaptation. No effect was found for barbiturates and ketamine. It seems unlikely that metabolites play a role in the observed phenomena. A literature survey reveals that several studies on dark adaptation or visual pigment regeneration might have suffered from influences of the anesthetic used. The cause of the phenomenon might lie either in anesthetics-induced membrane changes or in hindrance of the isomeration of 11-trans retinal to 11-cis retinal.