title: Seasonal and diurnal variations of ocular pressure in ocular hypertensive subjects in Pakistan.
abstract: BACKGROUND
  Studies have been shown that intraocular pressure (IOP) shows a diurnal variation in ocular hypertensive subjects, but the amount of change differs from study to study. In recent years it has been noted that intraocular pressure is a dynamic function and is subjected to many influences both acutely and over the long term. The variability in the results may be due to negligence of factors that can affect IOP. Moreover, seasonal variations in the ocular hypertensive subjects have never been described. After placing control on those factors that can affect IOP, this study investigated seasonal and diurnal variations in IOP of ocular hypertensive subjects.
  
  
  METHODS
  IOP was measured each month over the course of 12 months with the Goldmann applanation tonometer in 91 ocular hypertensive male subjects. To see the diurnal changes, subjects were asked to stay in the hospital for 24 hours.
  
  
  RESULTS
  The average IOP in the winter months was higher than those in spring, summer, and autumn. The IOP difference between winter and summer was (mean +/- sem) 2.9 +/- 0.9 mmHg (p < 0.001). The peak of mean IOP in diurnal variation curve (25.7 +/- 1.2 mmHg) appeared in the morning when the subjects had just awaken. The mean diurnal variation was found to be 4.2 +/- 0.6 mmHg (p < 0.001).
  
  
  CONCLUSIONS
  This study confirms that seasons influence IOP and it shows diurnal variations. As compared to other nations, diurnal variations in ocular hypertensive subjects seem to be somewhat less in Pakistan. Knowledge of the seasonal and diurnal variations in IOP may help glaucoma screeners.
authors.affiliation: Physiology Department, Jinnah Postgraduate Medical Centre, Karachi, Pakistan.
authors.forename: I A
authors.initials: IA
authors.lastname: Qureshi
authors.forename: R X
authors.initials: RX
authors.lastname: Xiao
authors.forename: B H
authors.initials: BH
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: D W
authors.initials: DW
authors.lastname: Xiang
authors.forename: J L
authors.initials: JL
authors.lastname: Hui
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology*; D010154:Pakistan; D012621:Seasons; D014065:Tonometry, Ocular