Imaging devices fail to pick up RNFL defects

Various imaging devices fail to identify localized retinal nerve fibre layer (RNFL) defects, according to a study published in the January issue of the British Journal of Ophthalmology.

Dr M T Nicolela of the Eye Care Center, Nova Scotia, Canada and colleagues had three masked observers assess eyes (51 with RNFL defects visible on optic disc photographs and 51 control) with confocal scanning laser tomography (CSLT), scanning laser polarimetry (SLP) and optical coherence tomography (OCT) to establish which device provided a more accurate image of localized damage.

The observers had the greatest degree of agreement of RNFL defect as displayed on OCT (kappa, 0.83), followed by SLP (0.69) and CSLT (0.64). At least two oberserves identified RNFL defects in 58.8%, 66.7% and 54.9% of images from CSLT, SLP and OCT, respectively. With CSLT, SLP and OCT, the observers rated 94.1%, 84.3% and 94.1%, respectively, of control eyes as normal.

The researchers deduced that between 20% and 40% of RNFL defects shown on colour optic disc photographs fail to be identified by CSLT, SPL or OCT. Of all three methods, SLP had the highest rate of both false-positives and correct RNFL defect identification.