Intraocular pressure is low in eyes with giant cell arteritis.

BACKGROUND: Although ocular ischemia occurs in giant cell arteritis (GCA), intraocular pressure (IOP) has not been systematically evaluated as a diagnostic sign. METHODS: We conducted a retrospective, case-controlled, observational study of IOP in patients with ocular manifestations of GCA (GCA patients), age-matched patients diagnosed with nonarteritic ischemic optic neuropathy (NAION patients), and age-matched patients with cataract (control patients). Medical records were examined for all consecutive patients with the diagnosis of GCA from 1995 to 2004 (n = 16) and NAION from 2002 to 2004 (n = 16) and for patient candidates for cataract extraction (n = 16). The eye intended for cataract extraction was chosen as the "affected eye" in the control patients. RESULTS: The mean IOP in the affected eye of 16 GCA patients was 11.9 mm Hg, significantly lower than the 15.1 mm Hg in affected eyes of age-matched NAION patients and 15.8 mm Hg in control patients (P = 0.002). At presentation, 5 GCA patients had IOP < 10 mm Hg (mean 6.8 mm Hg) without other signs of anterior segment ischemia. None of the NAION or control patients displayed such low IOPs. CONCLUSIONS: IOP was significantly lower in the patients with GCA than in patients with NAION or cataract. Hypotony occurred in one third of GCA patients without other signs of anterior ocular ischemia. These findings suggest that low IOP may be a distinguishing factor between GCA and NAION in patients with ischemic optic neuropathy, but evaluation of a larger group of patients is needed for confirmation.