Non-contact and Mackay-Marg tonometry: comparison in patients ages 7 to 85 years

In a sample of 212 eyes of patients referred to an ocular pathology clinic, measures of intraocular pressure (IOP) using the non-contact tonometer (NCT) and the Mackay-Marg tonometer were highly correlated (+0.91), the NCT MEASURES BEING LOWER BY AN AVERAGE OF 6.5 MM Hg. In a general optometry clinic, the mean IOP as measured with the NCT on 987 eyes of patients, ages 7 to 85 years, was 15.7 mm Hg (S.D.=3.5 mm Hg). Stability of IOP was age, found for this sample, is unexpected if IOP is proportional to systemic blood pressure which rises with age. Several hypotheses propose to explain the apparent inconsistency.