Autonomic Nervous System (ANS) Modulation to Control Intra‐ocular Pressure (IOP)

Abstract

Hypothesis IOP is set to a normal level by inflow and outflow dynamics of aqueous humor (AH) dependent on 2 main structures those are ‘Ciliary body’ and ‘Trabecular meshwork - Schlemm's canal’. Both have a great deal of regulation through the innervations of autonomic nervous system. Sustained elevation of IOP, usually results in Glaucoma. The only alterable parameter in glaucoma is intraocular pressure lowering, that is usually done by topical drugs/performing surgery. Keeping the impact of autonomic dysregulation on IOP homeostasis, our first study was planned in year 2012 in which we hypothesized that meditators would have a low mean IOP compared to non-meditators due to a state of parasympathetic dominance which is said to be established by meditation. This was followed by a second study (a clinical trial) started in 2017 in primary open-angle glaucoma(POAG)patients in which we hypothesized that the change in IOP between patients only on medications and patients on medications along with Yogic breathing exercises would be more in the latter group due to the induced parasympathetic dominance. Methods In the first study 3 groups were formed, viz. Group A: 20 Non-meditator persons with normal IOP Group B: 20 Non-meditators who had borderline IOP Group C: 20 Meditators who had normal IOP. Subsequently a battery of tests were undertaken to assess autonomic activity in all the groups after seeking their consent and making them familiar with the tests. In the second study, 90 patients with POAG were assigned to either the control or yogic breathing exercise group. In the latter group, yogic breathing was practiced daily for 6 months. We measured the intraocular pressure at presentation and subsequently after 1, 3, and 6 months. Results In the first study, the values observed in different tests in meditator group (Group C) showed parasympathetic dominance and decreased sympathetic drive, in comparison to both subgroups of non-meditators (Group 1 & Group 2). While, in the second study, compared with the ‘only-medication’ group, the ‘yogic breathing exercise’ group had significantly lowered intraocular pressure (right eye: 20.85±3.39 to 14.90±2.86mmHg; left eye: 20.30±4.12 to 14.25±3.85mmHg; P<0.001). Conclusions Both the studies concluded that in clinical practice regular meditation in ‘glaucoma suspect’ & ‘ocular hypertensive’ patients can bring down IOP due to improved parasympathetic tone and reduced sympathetic tone. Additionally, in POAG patients, yogic breathing exercises can reduce intraocular pressure and can therefore be recommended as an adjuvant therapy.