Experimentally reduced perfusion of one eye impairs retinal function in both eyes

The oscillatory potential index of scotopic white flash electroretinograms is reversibly enhanced in the contralateral eye when the ocular perfusion pressure (OPP) to the test eye is transiently reduced. A transient increase in the intraocular pressure (IOP) and decrease in the OPP in the test eye induced quantifiable vascular changes in the optic nerve head of the contralateral eye. We explored this contralateral phenomenon looking at ganglion cell function in both eyes during elevated IOP and decreased OPP in the test eye only. Our specific objective was to characterize the effects that transient hypoperfusion had on the neural generators of the pattern-reversal electroretinograms (pERGs), the ganglion cells, and preganglion neurons.

A transient elevation in the IOP was sustained in 10 healthy subjects by scleral suction to reduce the baseline OPP by 15, 30, 45, and 60% for 2-min intervals. For each level of OPP, pERGs were evoked by a checkerboard with 75 minarc high-contrast black-white checks reversing at 5 Hz and recorded bilaterally using DTL fiber electrodes. The pERGs were also recorded immediately after removal of scleral suction and at 2-min intervals thereafter for an 8-min recovery interval.

The unilateral decrease in OPP differentially reduced the pERG in the test and contralateral eyes. The pERG for the test eye returned to baseline amplitude within 2 min of removing the suction cup. In contrast, the pERG in the contralateral eye remained below baseline throughout the entire 8-min recovery interval.

The observation of a bilateral decrease in the pERGs while the OPP was decreased in the test eye only suggested that these neuronal changes were modified at more central visual centers for retinal function to be compromised bilaterally. This latter effect may have been mediated by the transiently altered OPP or yet unknown neurohormonal mechanisms.