OCTA Biomarkers Predictive of an Early Anatomical Response to Bevacizumab in Diabetic Macular Edema

Abstract

Purpose : To identify biomarkers that may predict an early anatomical response to the treatment of diabetic macular edema (DME) with off-label intravitreal bevacizumab (IVB) by means of optical coherence tomography angiography (OCTA).

Methods : Patients with diabetic retinopathy (DR) who were beginning treatment for DME were recruited from Cairo University Hospital. Included in the study were 36 treatment-naïve eyes of 23 patients who underwent 6×6 mm OCTA (Optovue, Fremont, CA) imaging of the macula at baseline and after three-monthly IVB injections. Eyes that demonstrated evidence of an early anatomical response, consisting of a >10% decrease in central macular thickness (CMT) (n=18), were compared to eyes that failed to improve on treatment (n=18).

Results : At baseline, early-response eyes had worse starting best-corrected visual acuity (BCVA, logMAR 0.84±0.41 versus logMAR 0.51±0.15, p=0.003) and a larger CMT (490±135 µm versus 356±33 µm, p=0.001), but smaller foveal avascular zones (FAZ) (0.31±0.10 mm versus 0.41±0.10 mm, p=0.003) compared with eyes unresponsive to IVB. The vascular density in the foveal superficial capillary plexus, as well as the vascular density of the foveal deep capillary plexus, were also significantly greater in early-response eyes compared with eyes that were non-responders (24.86±6.90% versus 19.98±7.13%, p=0.045, and 32.30±4.88% versus 26.95±7.25%, p=0.037, respectively). Early-treatment response to IVB was predicted by starting CMT (r²=0.266, p=0.001), FAZ size (r²=0.234, p=0.003), and vascular density in the superficial parafovea (r²=0.217, p=0.004) and deep fovea (r²=0.157, p=0.037). Hierarchical regression was used to assess variables that might influence treatment outcome. Adding the superior parafoveal vascular density of the superficial capillary plexus on OCTA to the starting CMT increased the prediction of the change in CMT to adjusted r² = 0.480 (change in r² = 0.118, p = 0.010). Age, gender, starting visual acuity, type, and severity of diabetes were excluded owing to a lack of significant unique predictive ability in the stepwise regression.

Conclusions : Projection-resolved OCTA may be useful in predicting an early anatomical response of DME to treatment with IVB. Future advances in OCTA scanning technology may further increase the ability of this non-invasive tool to predict treatment outcome based on vascular features.

This is a 2021 Imaging in the Eye Conference abstract.