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.

HbA1c is used as an index to reflect the average blood glucose levels of the past 1-2 months. A study in which HbA1c and the incidence of diabetic retinopathy were observed in a cross-sectional manner reported that the risk of onset of diabetes was high when HbA1c was 6.0% or more and less than 6.5%. Several studies have compared the sensitivity and specificity of fasting plasma glucose (FPG) and HbA1c in diabetic retinopathy detection. Many cross-sectional studies have reported that HbA1c was able to detect diabetic retinopathy more accurately.

This study will include 50 eyes of diabetic patients divided into: Group 1: 25 eyes of diabetic patients with controlled HbA1c Group 2: 25 eyes of diabetic patients with uncontrolled HbA1c, in the Department of Ophthalmology, Sohag University Hospital.