Abstract
Purpose: :
To assess the repeatability and accuracy on the measurement of retinal Nerve Fiber Layer (NFL) thickness using the RTVue FD-OCT system (Optovue, Fremont, CA).
Methods: :
The study was conducted using the ONH scan protocol of the RTVue system. To evaluate repeatability, the Advanced Imaging for Glaucoma study (AIGS) dataset in the University of Southern California collected from 2006 to 2010 was used. Total 107 subjects with repeated ONH scans (37 normals and 70 perimetric glaucoma subjects) within the same visit were studied. One eye per subject was randomly selected and repeatability was assessed by the intraclass correlation coefficient (ICC). The measurements were obtained through a TSNIT graph sampled from the optic disc center with a diameter of 3.45mm divided into 8 sectors. To evaluate accuracy, the ONH scans acquired from both eyes of 29 normal subjects in Optovue normative database were studied. An experienced image processing expert manually delineated the NFL inner and outer boundaries. The manual drawings were further verfified by two other experts. Accuracy was assessed for NFL inner and outer boundaries and the NFL thickness by computing the average differences of the results obtained from the automatic algorithm and those from the manual drawings, respectively.
Results: :
The repeatabilities based on the ICC of the NFL thickness measurements for normal and (perimetric glaucoma) subjects are: temporal quadrant 0.94(0.90), superior quadrant 0.89(0.96), nasal quadrant 0.90(0.92), inferior quadrant 0.89(0.97), upper hemisphere 0.93(0.97), lower hemisphere 0.92(0.97), and Overall average 0.96(0.98). The accuracies for NFL inner, outer boundaries and NFL thickness are: 1.68µm±2.4 µm, 4.23µm±6.54 µm, and 2.55µm±6.84 µm, respectively.
Conclusions: :
The NFL thickness measurement with RTVue is highly repeatable for both normal and glaucomatous eyes. Accuracy is within 3 microns on average indicating close agreement with using human boundary drawing as reference standard.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • imaging/image analysis: clinical