An objective method to define outlier optical coherence tomograms and repeatability of retinal nerve fibre layer measurements
Article first published online: 2 SEP 2004
Acta Ophthalmologica Scandinavica
Volume 82, Issue 5, pages 535–543, October 2004
How to Cite
Bergamin, O., Anderson, S. C. and Kardon, R. H. (2004), An objective method to define outlier optical coherence tomograms and repeatability of retinal nerve fibre layer measurements. Acta Ophthalmologica Scandinavica, 82: 535–543. doi: 10.1111/j.1600-0420.2004.00316.x
- Issue published online: 28 SEP 2004
- Article first published online: 2 SEP 2004
- Received on December 16th, 2003. Accepted on June 7th, 2004.
- optical coherence tomography;
- retinal nerve fibre layer;
- optic neuropathy;
- filtering method
Purpose: To compare the variation in thickness and reflectivity of the retinal nerve fibre layer (RNFL), circumferentially and on repeated testing.
Methods: In 24 normal eyes and 38 eyes with different optic neuropathies or retinopathies, third-party optical coherence tomography (OCT) software defined the RNFL border based on the reflectivity pattern across the retina and also provided measurements of the mean reflectivity and total retinal thickness in addition to RNFL thickness. A new Gaussian filtering method was implemented so that the weight of the applied filter was varied for each of five individually repeated scans until an optimum weight filter was determined.
Results: The scans requiring the highest weight filter could be identified as ‘outlier’ scans that contained measurement or alignment artifacts. There was no difference in the weights of filtering needed for normal and abnormal eyes. The RNFL thickness and reflectivity, and retinal thickness were highly correlated with one another in normal and abnormal eyes.
Conclusions: A new Gaussian filtering routine was devised that not only defined the most reproducible substructure of the RNFL for a given patient's eye, but also provided a new method of quantifying measurement variability and identification of scans with measurement or alignment artifacts.