Postural changes in intraocular pressure are associated with asymmetrical retinal nerve fiber thinning in treated patients with primary open-angle glaucoma

Abstract

To determine if asymmetrical postural change-induced elevations in intraocular pressure (IOP) in eyes of patients with primary open-angle glaucoma (POAG) were associated with asymmetries in functional and structural damage. Enrolled were 132 eyes of 66 patients with POAG (male/female = 22/44, age = 55.2 ± 13.4 years). IOP was first measured in a seated position and then in a supine position at 10-minute intervals over a 60-minute period using a TonoPen XL. The Humphrey visual field 30-2 program and a fast retinal nerve fiber layer (RNFL) thickness acquisition protocol of Stratus optical coherence tomography (OCT) were performed. Mean deviation (MD) and average total RNFL thickness were compared between eyes with the greater magnitude of postural change-induced IOP elevation (ΔIOP) and those with the smaller magnitude of ΔIOP. The MDs of the eyes with larger ΔIOP (6.21 ± 3.18mmHg) and smaller ΔIOP (3.02 ± 0.37mmHg) were -12.31 ± 7.63dB and -9.67 ± 6.80dB respectively (p = 0.0176). The average total RNFL thickness was 64.33 ± 17.83 μm in the former and 68.56 ± 15.10 μm in the latter (p = 0.049). The MDs and RNFL thickness were not significantly different between the eyes that had higher and lower IOP values measured in the seated position. In patients with asymmetrical POAG, the magnitude of IOP elevation induced by postural changes may be related to differences in the severity of both functional and structural damage between the eyes.