Red blood cell deformability, aggregability and cytosolic calcium concentration in normal tension glaucoma

The aim of the study was to determine the role of some erythrocyte patterns (Red Blood Cell deformability, aggregability, cytosolic calcium concentration) in normal tension glaucoma (NTG), compared with primary open angle glaucoma (POAG) and normal subjects.

Ninety patients entered the study, divided in three groups: age and sex-matched, otherwise normal subjects (30 patients), POAG (30 patients) and NTG patients (30 patients). Hemorheological parameters (elongation index [EI] and aggregability half time [At1/2] were detected using a laser diffractometer system (Laser-assisted Optical Rotational Cell Analyzer [LORCA]). Cytosolic calcium levels were measured using spectrofluorimetry.

No significant difference in systemic variables and refractive error was found. Mean hematocrit level, cell volume, plasma protein level and coagulation factors did not show any statistical difference among groups and resulted to be in the range of normality. A significant decrease in EI measurements was demonstrated in the NTG group (p<0.001) only. Similarly, A-t1/2 measurements were significantly smaller in the NTG group than in the other groups (p<0.001). Cytosolic calcium levels were significantly higher in the NTG group than in the other groups (p<0.001) and they were correlated to the elongation index for each group and overall (r=-0.756, p<0.001).

A significant decrease of erythrocyte deformability and increase in aggregability was found in NTG patients. These alterations seem to be inversely related to the intracytosolic calcium levels and they were not found in POAG patients and controls. Those results may contribute to understand the pathogenesis of normal tension glaucoma, suggesting a possible role played by red blood cells.