Significance of intraocular pressure measurement in systemic hypertension.

In normotensive subjects no differences were found between morning and afternoon measurements of (i) mean level of intraocular pressure (IOP), (ii) variance of IOP, and (iii) rise of IOP associated with lying down. Conversely, in subjects with untreated hypertension ( UH ) morning values of (i), (ii), and (iii) were all significantly elevated. Within each group morning and afternoon levels of systolic blood pressure (BP) remained constant but in UH the morning variance of systolic BP was elevated in proportion to the degree of hypertension. This disparate elevation resulted in highly significant correlations between levels and variance of systolic BP and IOP in the morning. These correlations were weaker or absent in the afternoon, and in normotensive persons at both times. These observations may explain the tendency of retinal vein occlusion to occur in the morning. Their relationship to the vascular changes of hypertension pose a problem for future study.