Purpose
To determine the interobserver and intraobserver reproducibility of different optic nerve head (ONH) parameters measurements performed by enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT) in a population with and without glaucoma.
Methods
We prospectively enrolled glaucomatous patients (glaucomatous optic neuropathy and reproducible visual field defect) and healthy individuals from August 2012 to October 2012. Those with significant media opacity or any ocular disease (besides glaucoma) were excluded. All participants underwent EDI-OCT (SD-OCT; Spectralis®, Wavelength: 870nm; Heidelberg Engineering Co., Heidelberg, Germany). The following ONH parameters were evaluated: lamina cribrosa and pre-laminar neural tissue thicknesses, scleral canal diameter (Bruch’s membrane opening) and cup depth. To examine the inter-observer reproducibility, two independent examiners assessed all images. To examine the intraobserver repeatability, each examiner evaluated each set of images twice. For each EDI-OCT parameter, repeatability and reproducibility were was assessed using within-subject standard deviation (Sw) and coefficient of variation (COV; 100%×Sw/overall mean), repeatability coefficient (RC; 1.96x√(2S2w) or 2.77 Sw), intraclass correlation coefficient (ICC; measurement of inter-rater reliability; set for absolute agreement) and Kappa (inter-rater agreement).
Results
A total 19 eyes of 19 patients were included. Overall, all ONH parameters assessed by EDI-OCT showed good repeatability results (Sw range, 4.7 - 19.1 µm; COV range, 0.55% - 7.3%; RC range, 13.1 - 52.9 µm). Judged by the COV, scleral canal diameter had the best and lamina cribrosa thickness had the worst intraobserver repeatability. Judged by the ICC (range, 0.70 - 0.99) and kappa values (range, 0.39 - 0.78), scleral canal diameter and cup depth had the best and lamina cribrosa thickness had the worst interobserver reliability and inter-rater agreement.
Conclusions
Based on manual measurements performed by experienced examiners, most ONH parameters assessed by EDI-OCT showed good intraobserver and interobserver reproducibility. Best results were found for pre-laminar tissues and landmarks compared to deeper ONH structures, such as the lamina cribrosa.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
627 optic disc •
577 lamina cribrosa