Precision of pachymetric measurements with scheimpflug : placido disc corneal opography and comparison of these measurements with ultrasonic pachymetry

Abstract EN

Back ground: Several devices with different physical bases have been developed for the clinical measurement of corneal thickness, they classified into 4 categories: Scheimpflug photography based, Slit –Scanning topography, optical coherence tomography (OCT) based and ultrasound (US) based.

Objective:To evaluatethe precision of the new Scheimpflug –Placido disc corneal topography in measurement of corneal thickness and to compare the measured values with that obtained by US pachymetry.

Methods: Setting of this study is Lasik center in Eye Specialty Private Hospital.

Baghdad.

Iraq.Eyes of healthy subjects were examined with the Sirius topography.3 consecutive measurements of central (CCT)and thinnest (TCT) corneal thicknesses were obtainedand the measurements repeated within 1 week.

The within –subject standard deviation (Sw),test-retest repeatability ,coefficient of variation (CoV),and interclass correlation coefficient (ICC) were calculated to evaluate intra session repeatability and intersession reproducibility.

For US pachymetry (Tomey-SP 100) only CCT was measured.

Comparison ofthe measurements that obtained by the 2 devices done by paired t-test.

Results: The topography provides high intrasession repeatability with test-retest and CoV close to 6μm and 0.4%, respectively for both CCT and TCT.

The inter session reproducibility also high with test-retest and CoV close to 8μm and 0.5%, respectively.ICC was higher than 0.97 for repeatability and reproducibility .

Anarrow 95% limit of agreement was found between the pachymetry obtained by topography and US pachymetry measurements.

Conclusions :The topography has been used showed high intrasession repeatability and intersession reproducibility of CCT and TCT measurements in healthy eyes .Absence of statistically significant differences suggest that the topography -TCT and the US pachymetry - CCT can be used interchangeably in subject with normal cornea.

Financial Disclosure: No financial or proprietary interest in any material or method mentioned.