Agreement Between Spectral Domain and Time Domain Optical Coherence Tomography (OCT)

Normal Foveal Thickness

optical coherence tomography, spectral domain, time domain

Optical coherence tomography (OCT) is a well-established and safe technique that offers the possibility of visualizing retinal structure and measuring retinal thickness. Time-domain (TD)OCT is considered the gold standard technique for retinal thickness measurements. Spectral-domain (SD) OCT has to face the gold standard technique prior to obtain scientific and clinical consensus. In our study in healthy subjects foveal thickness will be measured with both TD and SD OCT , and the data will be compared to evidence any difference between the two retinal measurements techniques.

The study will be performed at the Ophthalmology Clinic of the University of Chieti-Pescara, Italy. Forty healthy individuals will be enrolled in this study. In the same session in one randomly selected eye of each subject three consecutive measurements of foveal thickness will be performed using both TD OCT and FD OCT. All measurements will be obtained by the same experienced examinator. Time domain optical coherence tomography images will be obtained from each eye after pupil dilation using the Stratus OCT system (version 4.1. Carl Zeiss Meditec, Dublin, CA). Spectral domain optical coherence tomography images will be obtained using the HRA-OCT Spectralis unit (Heidelberg Engineering GmbH, Heidelberg, Germany). All data will be analyzed with the statistical package MedCalc® version 8.1 for Windows (MedCalc®, Mariakerke, Belgium). The D'Agostino-Pearson test that computes a single P-value for the combination of the coefficients of Skewness and Kurtosis will be used to study the sample distribution. T-test will be used to compare means between Stratus and Spectralis measurements and orizontal and vertical measurements. To assess agreement between Spectralis and Stratus OCT foveal measurements the Bland and Altman plots of the agreement in foveal thickness will be used. For both orizontal and vertical foveal measurements the ratio (Spectralis/stratus OCT foveal thickness) will be plotted against the average of the two measurements.

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