title: Age-related changes in central and peripheral corneal thickness: determination of normal values with the Orbscan II topography system.
abstract: OBJECTIVE
  The thickness of corneal tissue is an important parameter in refractive surgery, Goldmann applanation tonometry, and corneal diseases. The purpose of the study was to record system-specific normal values with the Orbscan II system and to investigate the influence of sex and age on central and peripheral corneal thickness to characterize more precisely the anatomy of the cornea.
  
  
  METHODS
  The Orbscan II topography system is a computer-assisted slit-beam scanning technology that can map the anterior section of the eye. It was used to take 2 measurements at 10-minute intervals on 777 eyes of 390 normal white subjects ranging in age between 10 and 80 years. Two hundred forty-two participants were men and 148 were women. The central corneal thickness and the nasal, superior, inferior, and temporal peripheral corneal thickness at a distance of 3 mm from the center were analyzed. No correction factor was used. Using nonparametric test methods, we carried out a statistical analysis of the parameters of sex and age.
  
  
  RESULTS
  The mean central corneal thickness of all 777 eyes was 595 +/- 41 microm. No sex-specific central difference was identifiable (P = 0.33), there was no significant difference between the sides (P = 0.23), and no significant difference was found between the first and second measurement. The group of 10- to 39-year-olds had a mean central corneal thickness of 591 +/- 41 microm, whereas that of 40- to 80-year-olds was 600 +/- 39 microm, which was a significant difference (P = 0.03). The mean peripheral corneal thickness was 689 +/- 46 microm nasally, 688 +/- 42 microm superiorly, 667 +/- 40 microm inferiorly, and 655 +/- 42 microm temporally. Nasally and superiorly, we found a significant negative correlation with age (Spearman rank correlation, P = 0.02).
  
  
  CONCLUSIONS
  The normal values presented here are a suitable reference basis for future studies in whites. Peripheral corneal thickness is asymmetric and seems to undergo age-related anatomic changes. This information should be considered when planning penetrating keratoplasty and refractive surgery.
authors.affiliation: Department of Ophthalmology, University Hospital of Kiel, Kiel, Germany. fruefer@ophthalmol.uni-kiel.de
authors.forename: Florian
authors.initials: F
authors.lastname: Rüfer
authors.forename: Anke
authors.initials: A
authors.lastname: Schröder
authors.forename: Christine
authors.initials: C
authors.lastname: Bader
authors.forename: Carl
authors.initials: C
authors.lastname: Erb
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000886:Anthropometry; D002648:Child; D003315:Cornea / Q000033:anatomy & histology*; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D017678:Sex Distribution