Comparison of inner macular thickness and superficial macular capillary vessel density acquired using classic and high-definition optical coherence tomography angiography scans

Abstract

Background: In ophthalmology, thickness and vessel density (VD) measurements for the 6 x 6 mm inner macular retinal area have received increasing attention in glaucomatous progression research. For this area, the Angiovue optical coherence tomography system introduced a 304 x 304 A/B scans function (classic Angio Retina scan) in 2014, and a 400 x 400 A/B scans function (high-definition [HD] Angio Retina scan) in 2017. These scan types cannot be used in combination for the software provided for progression analysis.
Purpose: Since losing data for 3 years may negatively influence progression analysis, we investigated whether clinically significant differences exist between consecutive measurements acquired with these scan types on the same eyes.
Methods: As a part of our noninterventional prospective glaucoma imaging study, primary-open-angle glaucoma patients (POAG group), and ocular hypertensive and healthy control participants (structurally undamaged group) were imaged
using both the classic and the HD Angio Retina scans, respectively, without changing the patients’ position. High-quality images were obtained on 12 POAG eyes of 12 consecutive POAG patients, and 10 healthy and ocular hypertensive eyes of 10 consecutive participants before the data collection had to be suspended due to the new coronavirus epidemic.
Results: For Early Treatment Diabetic Retinopathy Study image area, the mean difference (classic minus HD value) was 0.02 ± 0.37 μm for inner retinal thickness (P = 0.869) and 0.33 ± 1.33 % (P = 0.452) for superficial capillary VD in the structurally normal group (between-methods difference: ≤ 0.8% of the respective normal value). In the POAG group, the corresponding figures were -0.07 ± 1.22 μm for inner retinal thickness (P = 0.854; between-methods difference: 0.6% of the normal value) and 1.12 ± 2.58 % for superficial capillary VD (P = 0.158; classic scan value minus HD scan value: 1.12 ± 2.58 %; 2.3% of the normal value).
Conclusion: Our results suggest that combined use of thickness and VD values for structurally normal eyes and thickness values for POAG eyes derived from classic and HD scans, respectively, for progression analysis can be reasonable since the differences between the corresponding values are small. However, combining the corresponding VD parameters for POAG eyes is useful only when the follow-up time before the scan type change is long enough to counterbalance the effect of the change on the result.