Abstract
Purpose: :
To determine the limits of the normal amount of interocular asymmetry in retinal nerve fiber layer (RNFL) thickness measurements obtained with StratusTM Ocular Coherence Tomography (OCT).
Methods: :
Peripapillary Standard and Fast RNFL scans performed by the StratusTMOCT with nominal diameter of 3.46 mm centered on the optic disc were performed on both eyes of 108 normal subjects.
Results: :
The mean +/- standard deviation of age of the subjects was 46.0 years (standard deviation 15.0, range 20 - 82). The 95th percentile for interocular difference was 10.1µm for Standard scan measurements and 10.5 µm for Fast scan measurements. Mean RNFL thickness correlated extremely well between the two eyes of subjects, with intraclass correlation coefficients (ICC) of 0.89 for both algorithms. ICCs were less strong and variability was greater for quadrant and clock-hour thicknesses.
Conclusions: :
Mean RNFL thickness between the two eyes of normal individuals rarely differ by more than 10.1 - 10.5 µm, depending on what scan algorithm of the StratusTM is used. Differences beyond this level suggest statistically abnormal asymmetry and may be suspicious for early glaucomatous optic neuropathy.
Keywords: nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)