Measurement of corneal thickness in glucoma patients

Background. For the past 5 decades, Goldmann's applanation tonometry has been the basis for measurement of intraocular pressure. In this process, it is assumed that the corneal architecture - and particularly corneal thickness - does not have significant influence on the applanation tonometry. The aim of this study was to assess central corneal thickness in patients with primary open angle glaucoma (POWG), normal tension glaucoma (NDG), and ocular hypertension (OHT) compared to the central corneal thickness of control subjects. Method. In 200 consecutive glaucoma patients corneal pachymetry was performed with the Orbscan II system and a pachymetry map was obtained. Simultaneously, corneal pachymetry was also performed in 200 age- and sex-matched control subjects. To avoid diurnal variations the pachymetry measurements were performed at the same time of the day. Results. The central corneal thickness (CCT) distribution turned out to be a near-Gaussian curve in patients with glaucoma and in the control subjects. The mean CCT in glaucoma patients was 561 +/- 49.4 mum with a minimum of 448 lam and a maximum of 732 pm. In control subjects the mean CCT was 555.9 +/- 34.6 mum with a minimum of 480 mum and a maximum of 635 mum. Further evaluation of CCT of glaucoma patients demonstrated that the CCT in patients with PCWG was 559.5 +/- 43.5 mum, inpatients with NDG was 530.3 +/- 51.1 mum and with OHT was 624.2 +/- 25.4 mum. Conclusions. Central corneal thickness in patients with OHT was significantly greater, and in patients with NDG significantly lower, compared to control subjects. In defining the desired intraocular pressure in glaucoma patients, in the future CCT measurements should be considered along with intraocular pressure measurement and visual field analysis.