Blood oxygen transport mechanisms at different stages of primary open-angle glaucoma

Glaucoma is one of the leading causes of irreversible blindness worldwide.
The aim of the study was to evaluate blood oxygen transport mechanisms at different stages of primary open-angle glaucoma (POAG).
The total number of study participants was 130, including 100 patients diagnosed with POAG stages I–IV and 30 indi­ viduals without glaucoma. Optical coherence tomography was used to assess choroidal thickness. Gasotransmitters (nitric oxide (NO) and hydrogen sulfide (H2S)) and blood oxygen transport parameters were analyzed in venous blood.
Progressive POAG was associated with a persistent decrease in choroidal thickness, an imbalance in gasotransmitter levels (increased nitric oxide and decreased hydrogen sulfide concentrations), increased hemoglobin affinity for oxygen, and a leftward shift of the oxyhemoglobin dissociation curve. Choroidal thinning was 10.8 % at stage II (p = 0.001) and 31.0 % at stages III–IV (p < 0.001) compared to the control group. Nitric oxide concentration increased with disease progression: by 30.2 % at stage I (p = 0.002), 38.6 % at stage II (p < 0.001), and 108.9 % at stages III–IV (p < 0.001) relative to controls. Hydrogen sulfide levels decreased: by 21.9 % at stage II (p = 0.034) and by 54.1 % at stages III–IV (p < 0.001) compared with individuals without the disease. The greatest reduction in real and standard p50, reflecting increased hemoglobin affinity for oxygen, was observed at stage II – by 10.1 % (p = 0.009) and 10.0 % (p < 0.001), respectively.
The study results demonstrate the complex and multifactorial pathogenesis of glaucoma, which is accompanied by specific structural and functional changes in blood oxygen transport mechanisms.

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