Purpose:
To investigate the impact of typical scan score (TSS) on peripapillary retinal nerve fiber layer (RNFL) distribution of healthy controls measured by scanning laser polarimetry (SLP) and optical coherence tomography (OCT).
Methods:
One-hundred twenty two healthy normals were recruited from the Erlangen Glaucoma Registry for this study. Standard static white on white perimetry, stereographic optic disc slides, scanning laser polarimetry (GDx VCC, Carl Zeiss Meditec, Inc., Dublin, CA) and high-resolution SD-OCT (Spectralis HRA+OCT, Heidelberg Engineering, Germany) were performed. The subjects were divided into four subgroups according to their TSS (very typical with TSS = 100, typical with 99 ≥ TSS ≥ 90, less typical with 90 ≥ TSS ≥ 81 and atypical with TSS < 80). Deviation from very typical normal values were calculated for each group. Mann-Whitney test was used to compare between groups. P < 0.05 was considered statistically significant.
Results:
RNFL thickness detected by SLP showed a systematic deviation around the optic disc that reached up to 33.7 µm for atypical scans if compared to healthy subjects with TSS=100. Out of 32 peripapillary sectors for SLP 2 nasal and 7 temporal sectors of the atypical group, 5 temporal sectors of the less typical group and 1 nasal sector of the typical group showed significantly (all P<0.001) higher RNFL values than the very typical group (Fig. 1A). Mild alterations of RNFL values were found for OCT, but did not reach statistical significance (Fig. 1B).
Conclusions:
The TSS is a useful parameter to detect atypical scans with artificial increase of peripapillary RNFL thickness in temporal and nasal sectors caused by atypical retardation patterns.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optic disc