Abstract
Purpose: :
To report the frequency and severity of optical coherence tomography (OCT) retinal thickness measurement errors and to describe parameters which predict these errors.
Methods: :
One eye from each of 200 consecutive patients undergoing Stratus OCT imaging with Radial Lines or Fast Macular Thickness–based acquisition protocols was selected for review by two graders. On each of the line scans, graders evaluated the position of the automated retinal boundary lines (inner retinal surface and RPE band) used by the OCT machine for thickness calculations, and graded the positioning on a 6–point subjective, categorical error scale to generate an error score. The presence of thickness errors was correlated with various parameters including the analysis confidence assessment reported by the OCT software, disease diagnosis, retinal morphologic features, standard deviation (SD) of the foveal center thickness (FCT), and the FCTSD/FCT ratio.
Results: :
Errors of retinal boundary detection and thickness measurement were observed in 92% of cases, but were severe in only 13.5% of cases. The identification of an error or low analysis confidence by the OCT software was strongly associated with the severity of the retinal thickness errors. A higher FCTSD/FCT ratio and presence of subretinal fluid were also associated with more severe errors. Retinal cysts and a diagnosis of retinal vascular disease such as diabetic macular edema were less likely to be associated with significant errors.
Conclusions: :
Retinal thickness measurement errors occur frequently with current OCT segmentation and analysis algorithms. Severe errors are more frequent in eyes with subretinal pathology, but are generally detected by the OCT software. A high FCTSD/FCT ratio (>0.1) may also alert the clinician to the possibility of thickness errors. Clinical studies, particularly those pertaining to subretinal diseases, should consider these errors when incorporating OCT imaging in the study design.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • retina