Relation Between Glycemic Control and Retinal Microvascular Changes in Diabetic Patients Using OCTA

Diabetes is one of the fastest growing diseases worldwide, projected to affect 693 million adults by 2045. Devastating macrovascular complications (cardiovascular disease) and microvascular complications (such as diabetic kidney disease, diabetic retinopathy and neuropathy) lead to increased mortality, blindness, kidney failure and an overall decreased quality of life in individuals with diabetes Diabetic retinopathy (DR) is the major ocular complication of diabetes mellitus, and occurs in about 30 to 40% of diabetic individuals. Globally, more than 100 million individuals are living with DR, and DR is a leading cause of blindness and visual impairment, especially among the working-age adult population. Fortunately, much of the visual loss from DR is preventable, and the rates of vision loss from diabetes and DR have steadily declined over the past few decades. Such improvements in visual outcomes for DR are multifactorial, and are mainly due to a combination of better systemic risk factor control, coupled with advances in ocular disease assessment, screening, imaging and treatment in recent years.

From a haemodynamic perspective, evidence suggests that there is an early reduction in retinal perfusion before the onset of diabetic retinopathy followed by a gradual increase in blood flow as the complication progresses. Early changes in the retinal microcirculation include disruptions in blood flow, thickening of basement membrane, eventual loss of mural cells, and the genesis of acellular capillaries. Endothelial apoptosis and capillary dropout lead to a hypoxic inner retina, alterations in growth factors, and upregulation of inflammatory mediators.

The retinal blood vessels provide the opportunity to study early structural and functional changes in the microvasculature prior to clinically significant microvascular and macrovascular complications of diabetes. Advances in digital retinal photography and computerised assessment of the retinal vasculature have provided more objective and precise measurements of retinal vascular changes.

Optical coherence tomography (OCT) is a non-contact imaging technique which generates cross-sectional images of tissue with high resolution. Therefore it is especially valuable in organs, where traditional microscopic tissue diagnosis by means of biopsy is not available-such as the human eye.

Optical coherence tomography angiography (OCTA) is a new non-invasive imaging technique that employs motion contrast imaging to high-resolution volumetric blood flow information generating angiographic images in a matter of seconds.