Abstract
Purpose :
The aim of the present study is to evaluate differences between Spectralis SD-OCT fovea to disc alignment technology (FoDi) versus anatomic positioning system (APS) in healthy population. The Spectralis SD-OCT FoDi system, using TruTrackTM technology, automatically tracks and aligns 12° circle scans with a center manually positioned on confocal laser image of the optic nerve head. APS aligns scans automatically in relation to the patient’s individual Fovea-to-Bruch’s Membrane Opening centers axis. Both improve reproducibility eliminating rotational artifacts during scanning
Methods :
Prospective observational study in 37 eyes of 20 healthy subjects without ocular disease. Each participant underwent a comprehensive ophthalmologic examination. Spherical equivalent inclusion criteria were between -5.0 D and +5.0 dioptres. Measurements of the peripapilar RNFL thickness were obtained, in one session, without pupil dilatation. The same experienced operator carried out all exams, and adjusted the automatic detection of Bruch’s membrane opening. All images with artifacts and errors on RNFL segmentation were excluded from the analysis.
Results :
RNFL average thickness measurements were 102.86±7.57 microns (FoDI) and 104.91±8.34 microns (APS) showing statistical significance (p=.039). Only superior temporal and inferior nasal RNFL diagram sectors showed no statistical significance (p>.05). Ocular torsion did not differ between both examinations (p=.886). Diameter discrepancies were very small, the mean diameter for the fixed 12° circles was 3.55 ± 0.12 mm, and the mean degree for the fixed 3.5 mm circles was 11.87±0.41°. The agreement among RNFL measurements obtained by the different protocols of the same instrument was investigated using regression analysis, Bland-Altman plots and a paired T-test.
Conclusions :
Our results indicate that Spectralis SD-OCT RNFL thickness measurements using FoDi and APS showed different values, so they are not interchangeable. Whereas the definitions of the diameters are different in both protocols, the position of the circles and their sizes are very similar and the underlying biological structure usually did not change abruptly. The major reason for changes in the measurements between these circles are vessels near section borders, which changes the section from one to the other circle or differences in the segmentation lines.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.