INTRODUCTION: As populations are adopting a Western lifestyle, with high intake of dietary sugar and fat and low physical activity, the risk of developing Type 2 Diabetes is only increasing dramatically. Diabetes leads to drastic alterations within the body, primarily leading to neuropathies, nephropathies and retinopathies. As the prevalence of diabetes increases, it is important to understand the threat that it poses to the retina, and ultimately, vision. OBJECTIVE: We plan to compare the retina of diabetic patients with retinopathies to normal, healthy patients to understand the differences between them. We will be using a novel imaging technique, called Laser Speckle Flowgraphy, which provides the Mean Blur Rate, a value directly related to the blood flow velocity within the retina, specifically the optic nerve head. Using the calculated Mean Blur Rate, this study will quantify baseline blood flows in patients with diabetic retinopathies. This project aims to understand and differentiate the Mean Blur Rate of healthy patients and diabetic patients, including inter-patient and intra-patient comparisons, as well as changes in the Mean Blur Rate over time. The potential influence of treatment factors, such as intravitreal injection treatment or laser treatment, or demographic factors, such as age and race, on the Mean Blur Rate of diabetic retinopathy patients will also be evaluated. By understanding the difference in the retinas of diabetic patients and healthy patients, we can work towards preventing the loss of vision and function. METHODS: A total of 25 Type 2 diabetic patients with a diabetic retinopathy equaling 46 eyes were compared to 20 healthy patients, equaling 40 eyes. We collected the Mean Blur Rate for comparison between the two populations. Data was compared with correlation, t-test and ANOVA studies to find whether demographic or treatment variables influenced the Mean Blur Rate of diabetic retinopathy patients. RESULTS: We found a difference between the Mean Blur Rate, and thus blood flow, between the retina of diabetic and healthy patients. Diabetic patients tended to have a lower flow, presumably attributable the effects of hyperglycemia on blood circulation. Diabetic patients also have a significant difference in the Mean Blur Rate between both of their eyes, indicating that their hyperglycemia may affect both eyes differently (p<0). There was significant variability within both diabetic retinopathy patients and normal, healthy patients (p<0 for healthy patients and p<0.001 for diabetic patients). This is expected as blood circulation can be affected by a variety of factors other than disease status. We also found that the MBR of diabetics who were treated with intravitreal injections was on average higher than those who had not received intravitreal treatment. (p<0.05) CONCLUSION: Our study highlights how diabetic retinopathy impacts retinal blood flow, as well as showcases how Laser Speckle Flowgraphy can be used as a reliable method to measure and compare retinal blood velocities. Further studies are needed to understand how exactly diabetes affects blood circulation, although several theories are currently available. We also found a relation between previous intravitreal injection history and the blood flow velocity, but other studies have had mixed results on how exactly these injections alter the blood flow within the retina. Future studies can be conducted to better understand this relationship and uncover whether the effect on blood flow velocity is related to the drug used for the intravitreal injection or some other factor.

PURPOSE: This study aims to quantify the retinal vascular blood flow in eyes affected by unilateral central retinal vein occlusions (CRVO) or branch retinal vein occlusions (BRVO). We created and explored a new, unitless metric for the severity of these diseases: relative blood flow (RBF). We then contextualized RBF in terms of patient demographics, ocular presentation and other systemic conditions, as well as explored its efficacy as a predictor of future outcomes. METHODS: Data was collected from 20 control subjects and 32 patients with clinically diagnosed retinal vein occlusions (15 CRVO and 17 BRVO). Laser speckle flowgraphy was then used to quantify retinal vascular blood flow in terms of mean blur rate, a metric shown to be highly heterogeneous between patients but fairly consistent in intra-patient repeated measurements over time. After confirming this and establishing a strong correlation between a healthy patient’s two eyes, we used an RVO patient’s fellow eye as a nondiseased expectation and presented relative blood flow as the ratio between their diseased and healthy eye. We then correlated this data with demographic variables and disease characteristics from patients’ medical history. RESULTS: We found an average blood flow decrease of 26% in CRVO eyes relative to healthy eyes in the same patients and an average decrease of 7% in BRVO eyes. In CRVO, duration of occlusion, central macular thickness, intraocular pressure, diabetes, previous laser and injection treatments, and an injection within three months after blood flow measurement were significantly associated with relative blood flow. In BRVO, no demographic variables or disease characteristics were significantly associated with relative blood flow. CONCLUSIONS: Relative blood flow represents a promising new, consistent and informative metric for quantifying the severity of unilateral retinal vein occlusions. With both descriptive and predictive properties in eyes with CRVO, future work should explore its great potential.