Amplitude of the ocular pneumoplethysmography waveform is correlated with cardiac output

Ocular pulse amplitude, the amplitude of the ocular pneumoplethysmographic waveform, is altered in several ophthalmologic diseases that disturb ocular blood flow, implying that ocular pulse amplitude may provide an estimate of ocular blood flow. Because ocular blood flow currently cannot be quantified in humans, two experiments were undertaken to evaluate the association of ocular pulse amplitude with total body blood flow.

In experiment 1, cardiac output was determined by cardiac catheterization in 181 patients who underwent OPG-Gee testing during the same hospitalization. In experiment 2, 110 instances of atrial arrhythmia captured on ocular pneumoplethysmographic tracings were evaluated for transient changes in heart rate (R-R ratio) associated with transient changes in ocular pulse amplitude (ocular pulse amplitude ratio).

In experiment 1, average ocular pulse amplitude in the two eyes (OPAAV) was significantly correlated with cardiac output/heart rate (r = 0.53; p < 0.0001) and cardiac index/heart rate (r = 0.43; p < 0.0001). In experiment 2, R-R ratio was significantly correlated with ocular pulse amplitude ratio (r = 0.85; p < 0.001).

These results show that ocular pulse amplitude, a physiological measurement obtained from the globe, is correlated with cardiac output. They imply that ocular pulse amplitude may provide a clinically useful estimate of at least the pulsatile component of ocular blood flow.