title: Relationship Between Nocturnal Intraocular Pressure Elevation and Diurnal Intraocular Pressure Level in Normal-Tension Glaucoma Patients.
abstract: OBJECTIVE
  We studied the relationship between nocturnal habitual position IOP elevation and diurnal IOP level in normal-tension glaucoma (NTG) patients.
  
  
  METHODS
  A total of 70 young NTG patients with a low diurnal IOP level (mean diurnal seated IOP < 15.0 mm Hg; low IOP group) and 79 age-, axial length-, and disease severity-matched NTG patients with a high diurnal IOP level (mean diurnal seated IOP ≥ 15.0 mm Hg; high IOP group) were recruited prospectively. Intraocular pressure was recorded 11 times over a 24-hour period by a single, well-trained ophthalmology resident using a hand-held tonometer.
  
  
  RESULTS
  The mean habitual position IOP during nighttime (14.2 mm Hg) was significantly higher than that of daytime (12.8 mm Hg) in the low IOP group (P < 0.001), whereas no such difference was found in the high IOP group (16.4 vs. 16.3 mm Hg, P = 0.706). The low IOP group showed an overall nocturnal acrophase in habitual-position IOP, with 11 patients (15.7%) having a diurnal, 30 (42.8%) a nocturnal, and 29 (41.4%) no evident acrophase. By contrast, the high IOP group showed no evident peak in habitual-position IOP, with 28 patients (35.4%) having a diurnal, 12 (15.2%) a nocturnal, and 39 (49.4%) no evident acrophase.
  
  
  CONCLUSIONS
  In NTG eyes with a low diurnal IOP, there are significant IOP increases at nighttime in the habitual position, whereas there is no significant nocturnal IOP elevation in NTG eyes with a high diurnal IOP.
authors.affiliation: Department of Ophthalmology College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Yeji
authors.initials: Y
authors.lastname: Moon
authors.affiliation: Department of Ophthalmology College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Da Woon
authors.initials: DW
authors.lastname: Jeong
authors.affiliation: Department of Ophthalmology College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Soa
authors.initials: S
authors.lastname: Kim
authors.affiliation: Division of Biostatistics, Center for Medical Research and Information, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Seungbong
authors.initials: S
authors.lastname: Han
authors.affiliation: Department of Ophthalmology College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kook
mesh_terms: D000328:Adult; D000368:Aged; D002940:Circadian Rhythm; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D057066:Low Tension Glaucoma / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014065:Tonometry, Ocular; D055815:Young Adult