The Intraocular Pressure/Pulse Amplitude Relation and Loss of Autoregulation in Ocular Diseases

Young healthy adult male subject (22-years old) with healthy optic discs, full central visual fields, and routine timeand pressuredependent differential threshold light sensitivities: The steady state intraocular pressures (IOPs) were 14 and 15 mmHg in left and right eyes, respectively, measured with the Goldmann tonometer. The mean minimal and maximal of the IOP waves, recorded with the Langham tonometer, were 12.4/14.4 and 12.4/14.4 mmHg in the left and right eyes, respectively. The pulse amplitudes (PAs) were 2.0 mmHg in both eyes and the corresponding pulsatile blood flows were 934 and 925 μ l min −1 . Figure 17.1 shows a representative segment of the IOP recording on the left eye of the seated subject. The shaded area indicates the four pulses, which have been analyzed and tabulated below the recording. The recording shows the modulation of the IOP wave with respiration and the presence of a cardiac dichrotic notch. The postural responses in the left and right eyes were 1.5 and 1.5 mmHg, respectively, which are well within the range for healthy eyes. The IOP/PA relations in pairs of eyes of this subject are shown in Fig. 17.2 . They were identical in pairs of eyes and showed the rapid decline of the PA with modest increased IOP, reflective of active vascular autoregulation. 17