Axial length in applanation tonometry

Abstract

PURPOSE: To investigate the clinical applicability of a physical principle that suggests that a large globe offers less resistance to applanation than a smaller one. SETTING: Referral practice, Bridgeport, Connecticut, USA. METHODS: The correlation between axial length and applanation tonometry in 513 adult eyes, arbitrarily chosen from a referral practice, was examined using regression analysis. RESULTS: A statistically significant negative correlation was found; that is, for every 1.0 mm increase in axial length, the tonometry value was 0.29 units lower (P =.0002). In women, the mean axial length was 1.04 mm shorter and the mean intraocular pressure 0.54 mm Hg higher than in men. CONCLUSIONS: Globe size influenced applanation tonometry readings. Hence, when the tonometry record does not fit the clinical findings, axial length measurement may help interpret its significance.