Abstract
Purpose: :
To evaluate the agreement between retinal nerve fiber layer thickness (RNFL) measurements and diagnostic ability for glaucoma detection of two different spectral domain optical coherence tomography (SD-OCT) devices in normal and glaucomatous eyes.
Methods: :
Cross-sectional study with prospective sampling. One eye of 16 healthy subjects, 14 glaucoma suspects and 15 glaucoma patients have been enrolled. Participants were scanned in 2 sessions (within 3 months) by trained operators using the Cirrus SD-OCT (Carl Zeiss Meditec, Dublin, CA) and Spectralis SD-OCT (Heidelberg Engineering, Heidelberg, Germany). The RNFL thickness was measured with Cirrus 200x200 Optic Disc Cube mode and Spectralis RNFL algorithm. Global and sectoral RNFL thickness were compared using paired t tests. Pearson correlation analysis and Bland-Altman plots of RNFL measurements and Kappa coefficient of normative classification were used to evaluate the agreement between the 2 OCT devices.The sensitivity and specificity of both OCTs were also calculated.
Results: :
Mean age was 57.78±10,49 years, 58.22±9.31 years and 60.29±24.24 years for the healthy, glaucoma suspects and glaucoma subjects respectively (p=0.90). The RNFL thickness measured by Spectralis OCT was significantly greater than that measured by Cirrus OCT (healthy and suspects, p<0.001; glaucoma, p=0.033). For Cirrus OCT, the average RNFL thickness was 94.31±7.59µm, 87.29±9.49µm and 69.87±9.89µm for the healthy, suspect and glaucoma groups respectively. For Spectralis OCT, the corresponding measurements were 102.60±9.63µm, 92.43±10.68µm and 73.31±10.91µm. Average RNFL thickness measured by Spectralis OCT and Cirrus OCT was highly correlated (r=0.95; p<0.001). There was good agreement between the normative classification of the 2 devices (k=0.60; p<0.001). Spectralis OCT demonstrated higher specificity (93.8% vs. 72.7%) than Cirrus OCT but lower sensitivity (93.3% vs 100%).
Conclusions: :
Preliminary results suggest there are significant differences in RNFL thickness between Spectralis OCT and Cirrus OCT despite a good correlation of RNFL thickness measurements. Spectralis OCT offers a high sensitivity and specificity.
Keywords: nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)