Abstract
Purpose: :
The purpose of this study was to compare choroidal thickness measurements and inter examiner reproducibility using two different spectral-domain optical coherence tomography instruments (SD-OCT) in healthy eye.
Methods: :
Two different OCT instruments (Spectral OCT/SLO [Opko/OTI, Inc., Miami, FL] and Spectralis HRA OCT [Heidelberg Engineering, Inc., Heidelberg, Germany]) were used to assess choroidal thickness in healthy subjects. 44 eyes of 24 healthy volunteers were examined on the same day with each machine. Two sections were obtained (one horizontal and one vertical) centered on the fovea. The method of choroidal thickness measurements described by Spaide (AJO, 2009;147(5):811-815) was used. All measurements were performed by two independent examiners. The reliability was evaluated by intra-class correlation coefficient (ICC).
Results: :
The mean age of healthy volunteers was 25.4 ± 4.8 years. Eleven eyes of six healthy volunteers were excluded from the comparison because the chorioscleral interface could not be visualized with Spectral SLO/OCT ; in this group the Spectralis HRA OCT with Enhanced Deep Imaging (EDI) the mean choroidal thickness was 565.7 ± 10.4 μm. For the other 33 eyes, the average choroidal thickness was 326.9 ± 56.6 μm and 346.1 ± 66.1 μm with Spectral OCT/SLO and Spectralis HRA OCT respectively. We observed a high inter-examiner reproducibility with both machines : 0.88 (95% confidence interval (CI), 0.72-0.95), and 0.90 (95% CI, 0.83-0.96), using Spectral SLO/OCT and Spectralis HRA OCT respectively. A subgroup analysis of eyes, according to their choroidal thickness measurements with Spectralis HRA OCT with EDI was performed : <200 μm, 200 to 400 μm and >400 μm. With the SLO/OCT over 400 μm, inter examiner reproducibility of measurements decreased.
Conclusions: :
Under 400 microns the Spectralis HRA OCT showed similar choroidal thickness values but significantly higher values than did the Spectral OCT/SLO (a mean difference of 19.2 μm). It seems to be emerging a correlation coefficient between the two machines but too low to allow an interchangeable use of both OCT. Moreover EDI mode allows a choroidal thickness measurements over 400 microns with a high inter examiner reproducibility.
Keywords: choroid • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • clinical (human) or epidemiologic studies: systems/equipment/techniques