Enhanced Physiological Stress Response in Patients with Normal Tension Glaucoma during Hypoxia

Line Marie Dalgaard,Miriam Kolko,Rupali Vohra,Niels H Secher,Jeppe Vibæk,Barbara Cvenkel,Lars Thorbjørn Jensen,Niels Vidiendal Olsen,Biju B Thomas

doi:10.1155/2021/5826361

Abstract

Purpose To investigate whether patients with normal tension glaucoma (NTG) show an enhanced stress response to reduced oxygen supply compared to age-matched healthy controls, measured by serum adrenaline and endothelin-1 (ET-1) levels and changes in distal finger temperature. Methods A thorough clinical characterization of patients with NTG and age-matched controls was performed prior to inclusion in the study. Twelve patients with NTG and eleven healthy controls met the inclusion criteria and were enrolled in the study. All subjects underwent a two-day investigation. Participants were randomly exposed to either hypoxia or normoxia during the first visit. Hypoxia or normoxia was induced for two hours through a tightly fitting face mask. In addition, the peripheral circulation was assessed with a thermographic camera. Blood samples were obtained before, during, and after hypoxia or normoxia to evaluate systemic stress molecules such as catecholamines and ET-1 levels. Results In patients with NTG, reduced oxygen supply induced an increase in peripheral blood adrenaline (p < 0.05) and a decrease during recovery (p < 0.01). A difference in distal finger temperature was shown in patients with NTG under hypoxia compared to normoxia (exposure: p < 0.05; recovery: p < 0.05). Hypoxia induced an increase in peripheral blood ET-1 levels in both groups (NTG: p < 0.01; controls: p < 0.05). Conclusion Patients with NTG had an enhanced physiological stress response as a consequence of hypoxia compared with age-matched controls. Although more studies are needed, the present study supports the involvement of vascular risk factors in the pathophysiology of NTG.

Highlights

Glaucoma is a progressive optic neuropathy characterized by loss of retinal ganglion cells (RGC) and their axons
Since we assume that all patients with glaucoma have multiple risk factors and since we were interested in studying intraocular pressure (IOP)-independent factors, we examined glaucoma patients with IOP within the normal range, where IOP is hypothetically a less significant risk factor
As we have previously reported, a significant decrease in pO2 and saturation during hypoxia was seen in both normal tension glaucoma (NTG) patients and healthy controls leading to sustained hypoxia in both groups within 6 minutes of breathing 10% oxygen. ere were no significant differences between the two groups at any time

Summary

Introduction

Glaucoma is a progressive optic neuropathy characterized by loss of retinal ganglion cells (RGC) and their axons. Along with the loss of RGC, the disease is accompanied by a gradual loss of the peripheral visual field [1,2,3,4]. Glaucoma is the most frequent cause of incurable blindness and is estimated to affect approximately 111.8 million people by 2040 [5]. Together with aging, increased intraocular pressure (IOP) is recognized as the most important risk factor. Patients may have an IOP in the normal range and still develop glaucomatous progression (normal tension glaucoma, NTG) [6]. Erefore, the only existing treatments for glaucoma are IOP-lowering strategies, glaucoma is a multifactorial disease with many different risk factors [7]. Us, identifying and characterizing other instigators are essential Patients may have an IOP in the normal range and still develop glaucomatous progression (normal tension glaucoma, NTG) [6]. erefore, the only existing treatments for glaucoma are IOP-lowering strategies, glaucoma is a multifactorial disease with many different risk factors [7]. us, identifying and characterizing other instigators are essential.

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Methods

Results