Abstract
Purpose :
OCT related measurement at posterior pole, although comparable across devices, cannot be used interchangeably as shown by various studies. We sought to compare the ganglion cell thickness measurements obtained using two OCT devices using the built-in machine software and also when the retinal location and foveal cutout diameter were matched.
Methods :
Seventy-six individuals (25 glaucoma (G), 26 retinal pathologies (R) and 25 normal (N)) were examined for the study (mean age 51.8 years and standard deviation (SD) 12.8). All participants underwent 12x9mm2 3D wide scan using the 3D OCT-1 Maestro spectral domain OCT (Topcon Corporation, Tokyo, Japan) and the Ganglion Cell Complex (GCC) scan protocol using iVue OCT (Optovue, Fremont, CA). The GCC measures obtained by Maestro and iVue were compared overall and in the superior and inferior 180 degree hemi retina. The GCC measures were also obtained simulating the iVue location (shifted 1 mm temporally and the fovea cutout increasing to 0.75mm radius) from the Maestro OCT. The agreement was evaluated using the Bland-Altman plots and 95% confidence intervals for the mean difference were calculated and paired samples t-test was utilized to calculate statistical significance between differences of means.
Results :
The mean GCC, overall, superior and inferior, as measured by Maestro and iVue OCT is given in the tables below. The GCC measured by Maestro with built-in functionality was greater than that measured by iVue (ranging from 7.7 to 10.8 microns). The mean difference in GCC data from the Maestro with iVue simulated location and fovea cutout and the iVue measurements is much lesser (ranging from -1.2 to +1.3 microns). The 95% confidence intervals indicate that although the GCC data from Maestro and iVue OCT is significantly different, the difference between iVue simulated data of Maestro and the iVue data is not clinically significant.
Conclusions :
The difference in GCC as measured by Maestro and iVue appears to be a function of differences in location and area measured and not due to differences in segmentation algorithms of the devices. The larger built-in measurements on the Maestro appear to result from increased retinal nerve fiber layer thickness contributions stemming from the Maestro measurement grid’s relatively closer position to the optic disc.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.