Macular Vascular Fractal Dimension in the Deep Capillary Layer as an Early Indicator of Microvascular Loss for Retinopathy in Type 2 Diabetic Patients

Abstract

Citation: Chen Q, Ma Q, Wu C, et al. Macular vascular fractal dimension in the deep capillary layer as an early indicator of microvascular loss for retinopathy in type 2 diabetic patients. Invest Ophthalmol Vis Sci. 2017;58:3785-3794. DOI:10.1167/ iovs.17-21461 PURPOSE. To determine the ability of fractal dimension to detect early changes in the retinal microvascular network imaged by optical coherence tomography angiography (OCT-A) in type 2 diabetic patients. METHODS.Sixty-seven patients with type 2 diabetic mellitus (DM) (48 with no diabetic retinopathy [DR], 19 with minimal DR) and 40 control subjects. Macular OCT-A images of the superficial and deep retinal capillary layers in a 2.5-mm diameter concentric annular zone (excluding the foveal avascular zone) were subdivided into six annular rings and four quadrants. A custom automated algorithm was developed to quantify the complexity and density of the two retinal capillary layers by fractal analysis.RESULTS. Compared to controls, the fractal dimensional parameter (D box ) of the two retinal capillary layers in most regions was significantly lower in diabetic patients with minimal DR (P < 0.05). The D box of the diabetic patients with no DR was also decreased in most regions of the deep retinal capillary layer (P < 0.05), but not in the superficial retinal capillary layer (P > 0.05). Based on the receiver operating characteristic curve analysis, the D box values for the deep retinal capillary layer had the highest index to discriminate diabetic patients with and without minimal DR from controls. CONCLUSIONS.Fractal dimension based on OCT-A has the potential to quantitatively characterize retinal microvascular changes in the early stage of DM. Changes in the fractal dimension in the deep retinal capillary layer could be an early indicator of microvasculature changes associated with retinopathy in type 2 diabetic patients.

Optical Coherence Tomography Angiography Quantitative Assessment of Exercise-Induced Variations in Retinal Vascular Plexa of Healthy Subjects

“…22 Fractal analysis has already been used to explore the retinal vasculature in several studies, using fundus photography, [23][24][25][26] FA, 27,28 or OCT-A. 29,30 To the best of our knowledge, there is no anatomic data available, analyzing the effects of physical exercise in healthy subjects, on the retinal VDs, FAZ area, and retinal vascular FD in vivo using OCT-A at the same time. Variations in microretinal vasculature, which might be expected, could have an impact on the results of the examination.…”

“…The OCT-A SCP and DCP flow images generated by automatic segmentation were extracted in raw format and further processed with ImageJ (http://imagej.nih.gov/ij/; Wayne Rasband, provided in the public domain by the National Institutes of Health, Bethesda, MD, USA). We used the macro design described in a previous study 31 and applied it into all OCT-A images.…”

“…Fractal analysis was performed on the total parafoveal area with a diameter of 3 mm, as in a previous study. 30 FDs of the SCP and DCP were compared before and after exercise.…”

Implication of Deep-Vascular-Layer Alteration Detected by Optical Coherence Tomography Angiography for the Pathogenesis of Diabetic Retinopathy

“…Some studies found a significantly decreased vessel density in both superficial and deep vascular layers in patients without DR [7, 9]; however, in three other reports, vessel density was significantly reduced only in the deep vascular layer [10-12]. Fractal dimension was also significantly reduced in both superficial and deep vascular layers of patients with type 2 diabetes without DR [13]. The number of microaneurysms in the deep vascular layer exceeded the number in the superficial vascular layer in patients with nonproliferative DR (NPDR) [14-16].…”

“…The macular nonperfusion area was significantly increased in both superficial and deep vascular layers in patients with NPDR compared to control subjects [14, 22]. Fractal dimension in patients with NPDR was decreased in both retinal vascular layers compared to control subjects [13, 25, 27]. In contrast, another group reported increased fractal dimension in both vascular layers of patients with NPDR compared to control subjects [23].…”