This study investigates heart rate variability (HRV) in patients with normal tension glaucoma (NTG) and healthy subjects after a cold provocation test (CPT). The aim is to compare HRV parameter shifts and assess the relationship between structural damage, circulatory parameters, and autonomic dysfunction in NTG. The study included 78 NTG patients and 60 healthy controls. HRV was assessed using CPT, and ocular blood flow was measured with color Doppler imaging (CDI). The study also evaluated ocular perfusion pressure (MOPP), optic nerve head, and retinal nerve fiber layer (RNFL) using spectral-domain OCT. The results showed that NTG patients exhibited a predominance of sympathetic activity after CPT, with reduced end-diastolic velocities in the central retinal artery and short posterior ciliary artery compared to healthy subjects. The main HRV parameter, SDNN, correlated with MOPP, SPCA EDV, and CRA EDV. Average daily diastolic BP correlated with RNFL thickness. NTG patients showed autonomic dysfunction, which increased in response to stress and was related to ocular blood flow and structural damage. The study found that NTG patients had a more pronounced sympathetic response to CPT compared to healthy subjects, with significant differences in parameters such as LF and LF/HF. These findings suggest that HRV parameters, particularly LF and LF/HF, could be useful in the diagnosis of NTG. The study also found that NTG patients had reduced retrobulbar blood flow compared to healthy subjects. The results indicate that autonomic dysfunction plays a significant role in the pathogenesis of NTG and that HRV assessment could be a valuable tool in glaucoma diagnostics and monitoring. The study has limitations, including the lack of analysis of disease progression and test-retest variability. However, it is the first study to demonstrate a high correlation between local blood flow and HRV parameters in NTG.This study investigates heart rate variability (HRV) in patients with normal tension glaucoma (NTG) and healthy subjects after a cold provocation test (CPT). The aim is to compare HRV parameter shifts and assess the relationship between structural damage, circulatory parameters, and autonomic dysfunction in NTG. The study included 78 NTG patients and 60 healthy controls. HRV was assessed using CPT, and ocular blood flow was measured with color Doppler imaging (CDI). The study also evaluated ocular perfusion pressure (MOPP), optic nerve head, and retinal nerve fiber layer (RNFL) using spectral-domain OCT. The results showed that NTG patients exhibited a predominance of sympathetic activity after CPT, with reduced end-diastolic velocities in the central retinal artery and short posterior ciliary artery compared to healthy subjects. The main HRV parameter, SDNN, correlated with MOPP, SPCA EDV, and CRA EDV. Average daily diastolic BP correlated with RNFL thickness. NTG patients showed autonomic dysfunction, which increased in response to stress and was related to ocular blood flow and structural damage. The study found that NTG patients had a more pronounced sympathetic response to CPT compared to healthy subjects, with significant differences in parameters such as LF and LF/HF. These findings suggest that HRV parameters, particularly LF and LF/HF, could be useful in the diagnosis of NTG. The study also found that NTG patients had reduced retrobulbar blood flow compared to healthy subjects. The results indicate that autonomic dysfunction plays a significant role in the pathogenesis of NTG and that HRV assessment could be a valuable tool in glaucoma diagnostics and monitoring. The study has limitations, including the lack of analysis of disease progression and test-retest variability. However, it is the first study to demonstrate a high correlation between local blood flow and HRV parameters in NTG.