title: Effects of aging on 24-hour intraocular pressure measurements in sitting and supine body positions.
abstract: OBJECTIVE
  To evaluate how aging alters 24-hour measurements of intraocular pressure (IOP) in the sitting and supine body positions.
  
  
  METHODS
  Fifteen older volunteers with healthy eyes (ages, 53-71 years) were each housed for 1 day in a sleep laboratory. An 8-hour accustomed sleep period was assigned to each subject. Every 2 hours, measurements of IOP were taken in the sitting and supine positions. Sitting and supine patterns of 24-hour IOP were compared. Simulated 24-hour IOP rhythms in the same body position were determined using cosine fitting of individual 24-hour data. The average postural IOP effects during the diurnal/wake period and the nocturnal/sleep period were compared. Data from this group of older subjects were compared with previously collected data from 16 healthy younger subjects (ages, 18-25 years) under the same experimental conditions.
  
  
  RESULTS
  Within each age group, sitting and supine patterns of 24-hour IOP were similar and parallel. Compared to the younger subjects, the phase timing (simulated peak) of 24-hour IOP was significantly delayed for the older subjects in both body positions. The postural IOP effect for the older subjects was 4.7 ± 0.8 and 4.8 ± 0.8 mm Hg during the diurnal and nocturnal periods, respectively. These postural IOP effects were not significantly different from the postural effects in the younger subjects.
  
  
  CONCLUSIONS
  Although aging can significantly delay the phase timing of the 24-hour IOP pattern toward the diurnal/awake period, it may not affect the postural IOP effect during the diurnal and the nocturnal periods.
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California 92093-0946, USA.
authors.forename: Kaweh
authors.initials: K
authors.lastname: Mansouri
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: John H K
authors.initials: JH
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D016683:Supine Position / Q000502:physiology; D013997:Time Factors; D014065:Tonometry, Ocular; D055815:Young Adult