LOW-FREQUENCY SUBMICRON FLUCTUATIONS OF RED-BLOOD-CELLS IN DIABETIC-RETINOPATHY

Objective: To characterize cell membrane mechanical fluctuations of re d blood cells (RBCs) in patients with diabetic retinopathy. Methods: P oint dark-field microscopy-based recordings of these local displacemen ts of the cell membrane in human erythrocytes were compared between pa tients with severe proliferative diabetic retinopathy and healthy cont rols. The study was performed on discoid RBCs. Results: The average of the maximal displacement amplitude in the diabetic patients was 13.9% +/- 1.7% (236 +/- 29 nm) compared with 18.7% +/- 1.75% (318 +/- 30 nm ) for the controls (P<.001). The decrease of the RBCs' average displac ement amplitude was not correlated with the variation in negative curv ature of the central area of discoid cells. Conclusions: Microdisplace ments of the cell membrane, which reflect the bending deformability of the RBCs, are directly connected with its efficiency in passing throu gh capillaries narrower than its own diameter. These microdisplacement s were significantly reduced in patients with severe diabetic retinopa thy because of an increase in viscoelasticity of the cell membrane. Su ch reduced cell membrane microdisplacements, which reflect lower bendi ng deformability of the RBC, reduce the ability of the cell to enter a nd pass through small capillaries, increasing tissue ischemia and cons equently contributing to the develop: ment of diabetic retinopathy.