Tonography, Valsalva manoeuvre and central visual fields. A study of 429 patients.

Four hundred and twenty nine patients (846 eyes) referred to the glaucoma clinic at Concord Hospital between 1979 and 1989, were included in a prospective study. This study investigated the circulatory status of each eye during tonography, by using a modified Valsalva manoeuvre to induce changes in intraocular pressure (IOP) and amplitude of tonography pulse pressure (TPP). Of the large falls in IOP, 85% of the eyes had a Po/C greater than 150. The average IOP without medication, on the morning of the test, was 20 mmHg (2.67 kPa). Central visual field defects were found in 495 eyes, and these were far more prevalent in the Po/C greater than 150 category. An unexpected finding was the ratio of 67:33 right to left eyes in the Po/C less than 100 category. The commonest reasons for referral were intermittent rises of IOP, suspicious optic disc cupping, and the need to confirm a previously made diagnosis.