A pilot cross sectional study was conducted to investigate the role of red blood cells (RBC) deformability in type 2 diabetes mellitus (T2DM) without and with diabetic retinopathy (DR) using a dual optical tweezers stretching technique. A dual optical tweezers was made by splitting and recombining a single Nd:YAG laser beam. RBCs were trapped directly (i.e., without microbead handles) in the dual optical tweezers where they were observed to adopt a “side-on” orientation. RBC initial and final lengths after stretching were measured by digital video microscopy, and a Deformability index (DI) calculated. Blood from 8 healthy controls, 5 T2DM and 7 DR patients with respective mean age of 52.4yrs, 51.6 yrs and 52 yrs was analysed. Initial average length of RBCs for control group was 8.45 ± 0.25 μm, 8.68 ± 0.49 μm for DM RBCs and 8.82 ± 0.32 μm for DR RBCs (p < 0.001). The DI for control group was 0.0698 ± 0.0224, and that for DM RBCs was 0.0645 ± 0.03 and 0.0635 ± 0.028 (p < 0.001) for DR group. DI was inversely related to basal length of RBCs (p = 0.02). DI of RBC from DM and DR patients was significantly lower in comparison with normal healthy controls. A dual optical tweezers method can hence be reliably used to assess RBC deformability.

Citation: Bradley PD, Sim DA, Keane PA, et al. The evaluation of diabetic macular ischemia using optical coherence tomography angiography. Invest Ophthalmol Vis Sci. 2016;57:626-631. DOI:10.1167/iovs.15-18034 PURPOSE. The purpose of this study was to compare optical coherence tomography (OCT) angiography to standard fluorescein angiography (FA) in the grading of diabetic macular ischemia.METHODS. In our study, OCT angiography and traditional FA images were acquired from 24 diabetic patients. The level of diabetic macular ischemia in the superficial capillary plexus was graded with standard Early Treatment Diabetic Retinopathy Study (ETDRS) protocols and a comparison between conventional FA and OCT angiography was performed. The deep vascular plexus and choriocapillaris were also graded for macular ischemia. Additionally, flow indices were analyzed for all OCT angiography images. RESULTS.We identified moderate agreement between diabetic macular ischemia grades for conventional FA and OCT angiography (weighted j of 0.53 and 0.41). In addition, the intergrader agreement for the superficial, deep, and choriocapillaris scores was substantial (weighted j of 0.65, 0.61, and 0.65, respectively). Finally, the parafoveal flow indices were shown to have a statistically significant relationship with diabetic macular ischemia grades for the superficial capillary plexus (P ¼ 0.04) and choriocapillaris (P ¼ 0.036), with a trend toward significance for the deep capillary plexus (P ¼ 0.13).CONCLUSIONS. We demonstrated moderate agreement between diabetic macular ischemia grading results for OCT angiography and conventional FA using standard ETDRS protocols. We also showed that OCT angiography images could be graded for diabetic macular ischemia with substantial intergrader agreement.Keywords: diabetic macular ischemia, optical coherence tomography, fluorescein angiography D iabetic macular ischemia (DMI) is an important clinical feature of diabetic retinopathy (DR). It has been postulated that the selective loss of pericytes and thickening of the basement membrane in retinal capillaries occurs as a result of exposure to elevated blood glucose over an extended period of time.1 Clinically, DMI is defined by an enlargement of the foveal avascular zone (FAZ) and paramacular areas of capillary nonperfusion.2 In a previous paper, we have demonstrated that a large proportion (approximately 41%) of patients with DR in a tertiary hospital setting have some evidence of macular ischemia. 2 Of note, this study demonstrated that visual function was affected only in those with moderate to severe macular ischemia. 2 More recently, an analysis of the RIDE and RISE trials showed that patients with DMI at baseline progressed earlier to neovascular complications of DR during intravitreal ranibizumab treatment than those with normal perfusion at baseline. Therefore, baseline assessment of DMI when initiating ranibizumab therapy for diabetic macular edema (DME) has clinical implications and may be of practical importance to patients and physicians...

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