PULSATILE OCULAR BLOOD-FLOW IN PATIENTS WITH LOW TENSION GLAUCOMA

Measurements of the intraocular pressure (IOP) pulse and pulsatile ocular blood flow (POBF) have been made in 22 patients with bilateral low tension glaucoma (LTG) and 29 healthy subjects matched as closely as possible for age, refractive error, IOP, systemic pulse pressure, and heart rate. Recordings were made in both the standing and supine positions. The amplitude of the intraocular pressure pulse was significantly lower in patients with LTG (1.2, SEM 0.1 mmHg standing, and 1.3, SEM 0.1 mmHg lying) than in healthy subjects (1.9, SEM 0.1 mmHg standing, and 2.0 SEM 0.1 mmHg lying): p < 0.001 standing and p < 0.002 lying. Measurement of POBF also showed a significant reduction between the healthy subjects (428 (31) SEM-mu-l/min standing and 345 (28) SEM-mu-l/min lying) and subjects with LTG (301 (27) SEM-mu-l/min standing and 249 (24) SEM-mu-l/min lying), p < 0.005 standing and p < 0.02 lying. This represents a difference of approximately 30% between the two groups in either posture. A close non-parametric correlation existed between the level of IOP and the POBF (r = 0.75, p < 0.001 standing, and r = -0.55, p < 0.02 lying). Such a correlation was not present in the healthy subjects. A reduction in POBF occurred in both groups on assuming the supine posture (healthy subjects 83 (16) SEM-mu-l/min, LTG subjects 52 (17) SEM-mu-l/min). These figures represent reductions of 19% and 17% respectively in comparison with the standing value. The results lend further confirmation to the hypothesis that vascular factors are associated with low tension glaucoma.