title: Diurnal variation of human corneal curvature in young adults.
abstract: OBJECTIVE
  To elucidate the diurnal variation of human corneal curvature with regard to gender and menstrual cycle.
  
  
  METHODS
  Changes in corneal curvature and intraocular pressure (IOP) were measured over 24 hours in 14 young adults using corneal topography and a non-contact tonometer. In study 1, seven males and seven females (after menses) were measured. In study 2, four females out of the seven volunteers who participated in study 1 were measured again during menses.
  
  
  RESULTS
  The females after menses showed a remarkable diurnal variation throughout 24 hours. A significant difference between the light-wake periods and dark-sleep periods of 0.83 +/- 0.15 D was found (P < .01). Corneal curvature was significantly flatter during menses than after menses in the light-wake period (P < .05). In the males, no significant diurnal change (0.21 +/- 0.12 D) was measured in corneal curvature.
  
  
  CONCLUSIONS
  Diurnal variation of corneal curvature was significant, approximately 0.83 D in young females after menses, and corneal curvature became flatter during menses in young females. Diurnal variation of corneal curvature is an important parameter for planning refractive surgery and contact lens wear.
authors.affiliation: Doctor's Program of Medical Science, Kitasato University Graduate School, 1-15-1 Kitasato, Sagamihara-shi 228-8555, Japan. mm98030@ahs.kitasato-u.ac.jp
authors.forename: Tomoya
authors.initials: T
authors.lastname: Handa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Mukuno
authors.forename: Takahiro
authors.initials: T
authors.lastname: Niida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uozato
authors.forename: Shunichi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Kimiya
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D019781:Corneal Topography; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008597:Menstrual Cycle / Q000502:physiology