Normal tension glaucoma versus primary open-angle glaucoma - The autonomic perspective

Abstract

Background: Dissimilarities in the risk factors concerned with primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) suggest these two forms of glaucoma to be separate clinical entities, each having their own pathogenesis, yet the relationship between them is not clear convincing. Aims and Objectives: The aim of the study was to compare the autonomic activity between healthy controls, POAG, and NTG patients by heart rate variability (HRV). Materials and Methods: The study was conducted on 30 age- and sex-matched healthy controls (Group І), 30 patients with NTG (Group ІІ), and 30 patients with POAG (Group ІІІ) of age between 45 and 65 years. The basal HRV was analyzed at rest followed by stress tests, handgrip testing (HGT) and passive head-up tilt (HUT), and post recovery. Data obtained were statistically analyzed using SPSS 20. Results: Significant raised values of low frequency variables (LF [nu] [58.94 ± 6.556] and [73.39 ± 4.04]) in Group ІІ and Group ІІІ, respectively, as compared to Group І (52.13 ± 2.97). LF/HF ratio was significantly rise in Groups ІІ and ІІІ with P < 0.000 during HGT. LF/HF ratio was significantly high (P < 0.006) and (P < 0.004) in Groups ІІ and ІІІ, respectively, as compared to Group І during HUT. Conclusion: The above findings of HRV suggested greater withdrawal of vagal tone and persistently overdrive of sympathetic activity due to sympathovagal imbalance indicated ocular vascular alterations more in NTG than in POAG as compared to normal healthy subjects.