The retina is located at the back of the eye and contains light-sensitive cells and nerve cells. These cells are what allow your eyes to receive and organize the information that you see, but they are susceptible to a condition called hypoxia.
Monitor the amount of insulin produced by the beta cells in the pancreas (endogenous); in this case, a C-peptide test may also be done. Insulin and C-peptide are produced by the body at the same rate as part of the conversion of proinsulin to insulin in the pancreas.
A fall in blood glucose under about 4 mmol/l leads to a pronounced decrease in insulin secretion. The alpha-cells become active and deliver glucagon to the blood. Do not get the impression that there is a total secession of secretion of insulin or glucagon at high or low glucose levels.