Applanation tonometry and correction according to corneal thickness

Abstract

Purpose: In previous studies, it has been shown that the central corneal thickness influences the measurement values of applanation tonometry. The aim of this study is to answer the question as to which values and with what frequency the tonometer readings as based on corneal thickness have to be corrected in the patients attending an ophthalmic practice.

Subjects and methods: The corneal thickness was measured in 579 patients using ultrasound pachymetry under the conditions prevailing in a medical practice; from the thickness obtained, the correction values for intraocular pressure were calculated.

Results: Correction values of +/-2 mm Hg and above were found in half of the patients examined, and correction values of +/-3 mm Hg and above in a good quarter of the patients. The correction value was +/-4 mm Hg and more in every fifth patient.

Conclusions: Corneal thickness does, in fact, influence the results of applanation tonometry to a clinically relevant degree.