Neural effects of body inversion: photopic oscillatory potentials

The effect of alterations in retinal and choroidal circulation resulting from changes in body orientation were examined in 10 subjects with normal systemic and intraocular pressures. Body inversion resulted in an increase in the intraocular pressure with a concomitant increase in the ocular perfusion pressure. The effect of these pressure elevations was assessed by photopic oscillatory potentials (OPs). The trends in the change in OP amplitude with experimentally elevated ocular perfusion pressure varied across OP wavelets. OP-1 and the OP index exhibited a statistically significant decrease with an increase in ocular perfusion pressure, with OP-2 to OP-5 showing statistically insignificant reductions. Only OP-5 showed a significant decrease in implicit time with increased perfusion pressure. The magnitude of these changes were quite small despite a greater than 70% increase in the ocular perfusion pressure. Vascular autoregulatory mechanisms are hypothesized to be responsible for maintaining the OPs to within clinically normal levels.