The effects of altered retinal vascular perfusion pressure on the white flash scotopic ERG and oscillatory potentials in man

The oscillatory potentials (OPs) of the flash-elicited electroretinogram b-wave have been identified as sensitive indices of abnormalities within the retinal circulation. A recent study by Lovasik and Kothe has identified the rod system as being more vulnerable than the cone system to transient alterations of the retinal vascular perfusion pressure (RVPP). In view of these previous findings, we investigated the susceptibility of the scotopic OPs to altered retinal perfusion, in 10 normotensive paid volunteers between 21 and 31 years of age. A transient increase in RVPP was effected by body inversion, while a transient decrease in RVPP was obtained by suction ophthalmodynamometry. Group averaged data showed that OP-1 to OP-4 decreased in amplitude with either an increase or a decrease in RVPP. In contrast to all other OPs, OP-5 was reduced to a greater degree when RVPP was decreased and showed a pronounced gain in amplitude as RVPP was increased. Our study has isolated a component-specific vulnerability to altered retinal perfusion. This finding may be interpreted as indicating a different retinal site of origin for the generators of OP-5. The heightened sensitivity of OP-5 to alteration of the RVPP may offer diagnostic advantage for investigating chronic diseases causing retinal ischemia.