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P. Ceruti, R. Morbio, M. Marraffa, G. Marchini; Comparison Between Goldmann Applanation Tonometer and Dynamic Contour Tonometer in Normal and Glaucomatous Eyes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4844.
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Purpose: The purpose of this study was a comparison of intraocular pressure (IOP) measurements obtained by Goldmann Applanation Tonometer (GAT) and Dynamic Contour Tonometer (DCT) in healthy subjects, patients with Primary Open Angle Glaucoma (POAG) and patients with Primary Angle Closure Glaucoma (PACG). Methods: Fifty healthy subjects, fifty patients with POAG treated with topical drugs and fifty patients with PACG treated with miotic therapy were evaluated in a prospective, single–centre study. All subjects underwent following examinations: axial length and corneal curvature with an optical biometry system (IOL Master, Carl Zeiss AG), central corneal thickness (CCT) with an ultrasonic pachymeter (Pachette DGH 500, DGH Technology) and intraocular pressure (IOP) with GAT (Haag–Streit International) and DCT (Swiss Microtechnology AG) assembled on a slit lamp. All measurements were taken three times consecutively by the same examiner and the mean of three readings was used for each eye. Statistical analysis was performed with SPSS statistical software. Results: IOP readings, evaluated using the nonparametric Wilcoxon signed ranks test, were significantly higher (p<0,001) with DCT than with GAT; the analysis of three group together revealed a mean IOP difference (ΔIOP) of +2.6 mmHg ± 1.9 SD. In eyes whose mean CCT ranged between 530 and 580 µm, tested with an Independent Samples T–Test, we found a significant ΔIOP (p=0.009) between healthy subjects (+ 2.9 mmHg ± 1.3 SD) and patients with PACG (+2.05 mmHg ± 1.8 SD). IOP results on thinner corneas (<530 µm) didn’t show any significant difference between healthy and glaucomatous eyes. The evaluation of thicker corneas (>580 µm) revealed a significant ΔIOP (p=0.01) between normal subjects (+ 2.3 mmHg ± 0.8 SD) and patients with POAG (+0.7 mmHg ± 1.4 SD) and PACG (+1.3 mmHg ± 1.6 SD). Conclusions:IOP measurements were consistently higher with DCT than with GAT, with the highest significant ΔIOP between normal and PCAG eyes whose mean CCT ranged between 530 and 580 µm. The ΔIOP between GAT and DCT appeared significantly higher in healthy than glaucomatous subjects, either with open angle or angle closure phenotypes, also for those with a high CCT value (>580 µm). No significant difference was found between eyes with thinner corneas (<530 µm). In patients with POAG and PACG with a mean CCT value >580 µm, GAT and DCT results seemed to be equivalent.
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