Experiments involving stretching of the blood cells using laser light suggest that blindness in diabetes may be caused by stiffer blood cells.
When Leonie Watson. was diagnosed with Type 1 diabetes she was in her early childhood. Her blood sugar levels skyrocketed as her body stopped to produce insulin. In the middle of her twenties, something terrible happened - Leonie has seen a blood ribbon in her line of sight and her vision has started to worsen. She was totally blind before the age of 26.
Leonie as approximately 120 million other people in the world had signs of so-called diabetic retinopathy (DR) - a diabetes complication damaging the back of the eye (retina) - which is a leading cause of blindness in the world. What is worse, the first stage of DR develops with no-symptoms. During this stage, the arteries in retina are narrowing and become blocked. When the stage two starts, abnormal, burst-prone blood vessels are created and there is a very high risk that one’s vision may be permanently lost - even with advanced treatment methods.
However, why diabetics are prone to the vascular occlusion? This is where the interdisciplinary research. conducted by UCL physicists and physicians from Moorfields Eye Hospital comes into play. Researchers have hypothesized that the vascular occlusion in DR occurs because the blood cells in diabetes patients are stiffer, thus unable to deform properly and squeeze through the arteries in eyes. Deforming of blood cells is required as on average they are 8 micrometers in diameter whereas smallest blood vessels measure 5 micrometers in diameter. However, how deformable are blood cells and how to measure this?
Forget for a moment about the blood cells and consider a simpler problem: how do you measure how deformable is a spring? The simplest way of doing it is just to pull one end of a string when you hold the other and then observe how much it extends. If you pull the string hard and it stretches just slightly then it means that the string is not very deformable. Now, imagine that you do the same experiment just replacing your spring with a blood cell and your hands with two optical tweezers. Optical tweezers use highly-focused laser beams to exert very small forces on a microscopic object. Now, by holding one end of the blood cell with the first laser beam and pulling the second one to the other side you may stretch the blood cell! Interestingly, these experiments performed for blood cells of healthy and diabetics patients show that stiffness of the red blood cells for diabetes was larger compared to the healthy patients - with one in a million chance that it happened randomly. Furthermore, no other, statistically significant differences in biochemical or hematological properties of blood between diabetes and healthy patients group were found - which suggest that the mechanism described above is primary.
Concluding, diabetic retinopathy may be caused by stiffer blood cells in diabetes patients and this can be measured using optical tweezers. Optical tweezers allow for measuring the mechanical properties of many biological samples - which cannot be done using biochemical techniques - so that medical doctors and physicists should collaborate even more often.
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