Comparability of a Sample of Certified Schiotz Tonometers

Abstract

Introduction Any attempt to determine the prevalence of glaucoma with sufficient accuracy to permit legitimate geographic comparisons will require carefully standardized instruments and procedures. For such epidemiologic field studies the use of tonometers of established precision is a preliminary and fundamental requirement. Inconsistency among the recordings obtained from various Schiotz indentation tonometers has led to attempts to establish acceptable manufacturing tolerance. Largely through the extensive efforts of the Committee on Standardization of Tonometers of the American Academy of Ophthalmology and Otolaryngology, there has been considerable improvement in the uniformity of available instruments. Still, it is suggested that residual inconsistencies may exist in theory¹ and in fact.^2-4 Since the Epidemiology Branch of the National Institute of Neurological Diseases and Blindness proposes quantitative field investigations of the relative frequency of chronic simple glaucoma among selected populations, an examination of the comparability among a sample of Schiotz tonometers was undertaken. The