Abstract
Purpose::
The purpose of this study is to compare the newly released Spectral OCT/SLO (OTI, Toronto, Canada) with the Zeiss Stratus OCT (Carl Zeiss Meditec, Dublin, CA) with regards to the quality of the images obtained as well as the ease of use.
Methods::
A retrospective analysis was made of twenty five (25) patients with various retinal pathologies who were imaged with both the Stratus OCT and the OTI Spectral OCT/SLO in October and November 2006. Horizontal and vertical scans over the lesion were obtained with both machines. With the Stratus, 2mm crosshair scans were used to obtain these scans. For the OTI Spectral, the scan line was rotated manually to obtain the desired scans.Retinal thickness maps were also obtained from both machines. The "fast macular thickness" maps obtained using the Stratus OCT were taken from six 6mm radial scans taken consecutively in 2 seconds through a single point. The OTI Spectral "high quality (2s) zoomed retinal topography stack" captured 64 horizontal scans in raster fashion over an area of 5mm.
Results::
The horizontal and vertical scans obtained using the OTI Spectral machine were consistently better than those obtained with the Stratus OCT. The Stratus OCT was comparable to the OTI Spectral in identifying gross abnormalities such macular holes, RPE detachments and thick epiretinal membranes, but was often unable to detect more subtle changes, such as retinal folds, small intraretinal cystic changes, and posterior vitreous detachments. Retinal thickness maps obtained with the Stratus OCT covered a slightly larger area (6mm) and allowed zone analysis up to 6mm area. The OTI Spectral unit obtained thickness measurements on the central 5mm only when using the grid analysis. Zone analysis was confined to the central 3 mm. No pattern was found in the comparing the central 3mm thickness of both machines. Both machines were found to be comparable with regards to ease of use, testing time, and patient comfort.
Conclusions::
The OTI Spectral OCT/SLO longitudinal scan was superior to the Stratus OCT in detecting subtle retinal changes. For retinal thickness mapping, the OTI Spectral unit used more scans to obtain thickness measurements but covered a slightly smaller area. Differences in thickness measurements between the two machines were found but are difficult to interpret, as they may be due to the difference between the machines’ algorithms in calculating thickness, the slight differences in area imaged, or both.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical