Circadian Patterns of Intraocular Pressure Fluctuation among Normal-Tension Glaucoma Optic Disc Phenotypes

ObjectiveTo characterize the 24-h habitual-position intraocular pressure (IOP) patterns of optic disc phenotypes (ODPs) in untreated normal-tension glaucoma (NTG) and the relationships between nocturnal IOP elevation and various clinical factors.DesignProspective, cross-sectional, observational study.MethodsEighty-two NTG patients with focal ischemic (FI) ODP and 82 age- and disease severity-matched NTG patients with myopic glaucomatous (MG) ODP were recruited prospectively over 3 years. The IOP was recorded 11 times over a 24-hour (h) period by a single ophthalmologist using a hand-held tonometer (TonoPen®XL). A cosinor model was used to describe the 24-h IOP rhythm. Associations between nocturnal IOP elevation and both ocular and demographic variables were evaluated using the generalized estimating equation (GEE).ResultsMean habitual-position IOP was significantly higher during nighttime than daytime in the FI group (16.44 vs. 14.23 mmHg, P = 0.001) were independently associated with nocturnal IOP elevation.ConclusionsBased on 24-h habitual-position IOP data, FI is associated with significant nocturnal IOP elevation, while no such nocturnal IOP elevation is observed in MG ODP. In untreated NTG, there are also significant differences in the 24-h IOP pattern between FI and MG ODPs.