Abstract
Purpose: :
To understand the differences in the image quality parameters as provided by four different Spectral Domain Optical Coherence Tomography (SDOCT) devices, using a simulation of optical eye media disturbances with a set of artificial filters introduced within the scanning beam.
Methods: :
In two healthy volunteers b-scans of the macula were acquired using four SD-OCT systems (Cirrus, Carl Zeiss Meditec; RTVue, OptoVue; Spectralis OCT, Heidelberg Engineering; and 3D-OCT-1000, MarkII, Topcon). During scanning, a series of artificial filters were placed in front of the eye. Three effects were simulated: light attenuation (absorptive and reflective filters), refractive aberrations (defocusing lenses) and straylight (scattering filters). For the effects of the filters an earlier model was used, expressing their effective optical density, determined for the 830 nm central wavelength of the OCT (OD). All measurements were done twice by the same experienced examiner. The quality parameter of the OCT images as reported by the different devices was used for comparison.
Results: :
The provided parameters SS (Signal Strength) by Cirrus, Carl Zeiss Meditec, SSI (Signal Strength Index) by RTVue, OptoVue, Q-factor by 3D-OCT-1000, MarkII, Topcon and Quality by Spectralis OCT, Heidelberg Engineering, are not directly comparable.However, for each SDOCT device a linear relationship could be demonstrated between the OD of the filters and the parameter as reported by the device concerned.
Conclusions: :
Differences in reported OCT image quality parameters are hampering direct comparisons of the image quality between different SDOCT systems. Standardization is recommended in order to compare different devices and study results. Our advice is to use a measured attenuation of the OCT signal, while double passing through the eye, like optical density in this study.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: non-clinical