Comparison of macular thickness in diabetic patients acquired from optical coherence tomography mode and optical coherence tomography angiography mode in Cirrus HD-OCT 5000

Purpose
To compare macular thickness obtained using two different modes of image acquisitions with Cirrus HD-OCT 5000.
Methods
Patients with diabetes were recruited and macular thickness were obtained using optical coherence tomography (OCT) mode and optical coherence tomography angiography (OCTA) mode. The OCT mode involved a Macular Cube (512×128 pixels) centred on the fovea covering a 6 × 6 mm2 macular region. The OCTA acquisition involved scanning of a 6 × 6 mm² scan (350×350 pixels) centred on the fovea. Data was exported and compared according to the Early Treatment Diabetic Retinopathy Study (ETDRS) subfields. Fixation deviation was defined as the deviation of the foveal point from the grid center in the OCT scan and OCTA scan.
Results
Eighty-six diabetic patients were recruited had similar macular thickness in all ETDRS subfield except the superior outer sector. The 95 % limits of agreement between the two modes were within 9.7μm to -9.0μm. It took longer to complete each OCTA mode (median of 7.4 s) than the OCT mode (median time of 5.8 s) (Wilcoxon test, p < 0.001), but OCTA generated a smaller fixation deviation (median 68.8μm) than the OCT mode (median 103.0μm) (Wilcoxon test, p = 0.014).
Conclusions
Improved fixation in OCTA compared with OCT was evident, likely because of the faster scanning speed and higher sampling density of OCTA. Macular thickness was found similar. There appears no requirement to obtain macular thickness measurements using a separate OCT mode. This approach can reduce patient chair time, improve patient comfort, and streamline the clinical workflow.