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.

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The SCS is expandable and can recover to preinjection status after injected fluid is cleared by physiological processes. The injection-induced SCS expansion is volume-dependent, and the drug/dye retained in the SCS is formulation-dependent. The current injection technique with a volume of 20 μL or less is well tolerated in guinea pig eyes.

The structural characteristics of the outer retinal layers in primary open angle glaucoma (POAG) are still controversial, and these changes, along with those in the inner retinal layers, could have clinical and/or pathophysiological significance. A custom-built ultra-high resolution optical coherence tomography (UHR-OCT) combined with an automated segmentation algorithm can image and measure the eight intra-retinal layers. The purpose of this study is to determine the thickness characteristics of the macular intra-retinal layers, especially the outer layers, in POAG patients. Thirty-four POAG patients (56 eyes) and 33 normal subjects (63 eyes) were enrolled. Thickness profiles of the eight intra-retinal layers along a 6-mm length centred on the fovea at the horizontal and vertical meridians were obtained and the regional thicknesses were compared between two groups. The associations between the thicknesses of each intra-retinal layer and the macular visual field (VF) sensitivity were then analysed. POAG affected not only the inner retinal layers but also the photoreceptor layers and retinal pigment epithelium of the outer retina. However, the VF loss was correlated mainly with the damage of the inner retinal layers. UHR-OCT with automated algorithm is a useful tool in detecting microstructural changes of macula with respect to the progression of glaucoma.

Intraretinal thickness changes in asymptomatic patients could be prodromal events that indicate the imminent conversion to symptomatic patients with Leber's hereditary optic neuropathy.