Pathophysiology of Intraocular Pressure Increase and Glaucoma Prevalence in Thyroid Eye Disease: A Mini-Review

Abstract

The aim of this study was to assess the pathophysiological mechanisms leading to intraocular pressure (IOP) increase and to review the prevalence of glaucoma in thyroid eye disease (TED), an autoimmune reaction affecting extra-ocular muscles and intra-orbital content in thyrotoxicosis (Grave's disease, hyperthyroidism). We applied the modified Friedenswald's and Goldmann's equations to explain the mechanisms by which IOP increases in TED and gave a brief review of the literature. In TED, Friedenswald's equation explains the ultra-short term IOP increase observed when eyes deviate from their primary gaze position (eyeball compression by enlarged and infiltrated extra-ocular muscles). Goldmann's equation explains the long-term IOP increase seen in TED (episcleral venous pressure elevation secondary to intraorbital content and pressure increase). Most studies did not find a significant increase in glaucoma prevalence in patients with TED. In TED, glaucoma prevalence does not seem to be significantly increased and, from a pathophysiological standpoint, the long-term IOP increase is essentially due to episcleral venous pressure elevation.