Dependency of intraocular pressure on body posture in glaucoma patients : New approaches to pathogenesis and treatment

Abstract

Human intraocular pressure (IOP) depends on the position of the head in relation to the body in space. Physiologically, the IOP increases in alying position compared to an upright posture. Microgravity in space also appears to cause an increase in intraocular pressure, accompanied by other ophthalmological changes, which are summarized under the term spaceflight associated neuro-ocular syndrome (SANS). Bed rest studies are being carried out to investigate the effects of weightlessness on the human body. So here there is an intersection between research into SANS and glaucoma. Increased intraocular pressure remains the most important risk factor for glaucoma development and progression that can be influenced by treatment. The influence of position-dependent IOP fluctuations on glaucoma is still not sufficiently understood. A literature search was carried in PubMed on the subject of IOP fluctuations related to posture. Analysis and evaluation of the published study results and a summary of available clinical data. The increase in IOP when changing from aseated to alying body position is greater in glaucoma patients with an increase of up to 8.6 mm Hg compared to healthy subjects with an increase up to 5 mm Hg. In small pilot studies the increase in lying IOP in some glaucoma patients and healthy volunteers could be attenuated by elevation of the head by 30%. Alower compartmental pressure in the subarachnoid space has been associated with glaucoma and may represent arisk factor for glaucoma development. Not only the level of IOP but also IOP fluctuations were associated with an increased risk of disease progression. The clinical significance of IOP peaks during sleep on glaucoma is still not sufficiently understood. New methods for continuous IOP measurement offer promising opportunities for further research into the importance of IOP fluctuations related to changes of body and head posture.