Abstract
Purpose: :
To evaluate the intravisit repeatability of Optic Nerve Head (ONH) parameters measured by CirrusTM HD-OCT (Carl Zeiss Meditec) in healthy subjects.
Methods: :
Thirty-two eyes of 32 healthy subjects (mean age: 56 ±19 years) were prospectively enrolled. For each subject, three scans were acquired on the same day with the Cirrus (software version 3.0.0.64) using the Optic Disc Cube 200x200 protocol. The ONH analysis was performed on this data set using the Cirrus 5.0 pre-production software. The ONH parameters reported result from a fully-automatic algorithm that defines both the disc and cup margins within the 3d data cube. This disc margin is defined as the termination of Bruch’s membrane; the cup margin is defined indirectly as it is instead based on the measurement of the neuro-retinal rim as the nerve fibers exit the eye. Coefficient of variation (COV, %), test-retest repeteability (TRR) and intraclass correlation (ICC) were calculated for each measured parameter.
Results: :
COV and TRR were respectively 1.84% and 0.013 for average cup-to-disc ratio, 1.99% and 0.075mm2 for disc area, 1.96% and 0.051mm2 for rim area, 4.54% and 0.009mm3 for cup volume, 2.72% and 0.025 for horizontal cup-to-disc ratio, 3.42% and 0.028 for vertical cup-to-disc ratio, 2.94% and 0.033mm for horizonal rim thickness, 2.63% and 0.039mm for vertical rim thickness, and 0.98% and 0.029mm for average diameter. ICC was higher than 0.97 for all parameters.
Conclusions: :
In healthy subjects the ONH measurements provided by the Cirrus showed excellent repeatability. Comparison of these data to those previously published with StratusOCT suggests a remarkable improvement of intravisit repeatability for all ONH parameters.
Keywords: optic nerve • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)