Retinal circulation during a spontaneous rise of intraocular pressure.

The retinal haemodynamic changes occurring in an eye with a spontaneous elevation of intraocular pressure were investigated by bidirectional laser Doppler velocimetry and monochromatic fundus photography. At an intraocular pressure of 47 mmHg the blood velocity and volumetric blood flow rate were significantly smaller and arterial blood velocity pulsatility was significantly greater than normal. The corresponding 88% reduction in perfusion pressure was accompanied by a 67% reduction in total retinal blood flow, indicating that autoregulation is not efficient at this level of intraocular pressure. An Octopus visual field examination obtained immediately following blood flow measurements suggested that the central retina can preserve a fairly good function under a total retinal blood flow rate of about one-third of the normal value.