title: Age-related thinning of Bowman's layer in the human cornea in vivo.
abstract: OBJECTIVE
  To determine the thickness of Bowman's layer (BL) in vivo in a healthy population and to determine its variation with age.
  
  
  METHODS
  Eighty-two subjects aged 15 to 88 years with clear, healthy corneas were examined bilaterally with laser scanning in vivo confocal microscopy (IVCM). Bowman's layer thickness was determined from IVCM images of anterior and posterior BL boundaries. For a given eye, BL thickness was averaged across four central locations by two independent observers. In addition, central corneal thickness was measured by time-domain optical coherence tomography.
  
  
  RESULTS
  A significant negative correlation of BL thickness with age was found in right eyes (Pearson r = -0.579, P < 0.0001) and in left eyes (r = -0.558, P < 0.0001). Linear regression analysis yielded a decline in BL thickness of 0.06 μm per year. In 41 older subjects (mean age, 64.4 years), BL thickness was significantly thinner (mean ± SD, 8.6 ± 1.7 μm in right eyes) than that in 41 younger subjects (mean age, 31.6 years) (mean ± SD, 10.7 ± 1.6 μm in right eyes) (P < 0.001). No correlation of corneal thickness with age or of BL thickness with corneal thickness was observed. Strong intereye correlations in BL thickness (r = 0.771, P < 0.0001) and corneal thickness (r = 0.969, P < 0.001) were found.
  
  
  CONCLUSIONS
  Bowman's layer thins with age in the normal cornea, losing one-third of its thickness between the ages of 20 and 80 years. In vivo measurement of BL thickness by IVCM could aid in clinical assessment and planned treatments of the anterior cornea.
authors: Department of Clinical and Experimental Medicine-Ophthalmology, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors: Johan
authors: J
authors: Germundsson
authors: Georgios
authors: G
authors: Karanis
authors: Per
authors: P
authors: Fagerholm
authors: Neil
authors: N
authors: Lagali
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D050541:Bowman Membrane / Q000033:anatomy & histology*; D003315:Cornea / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D012044:Regression Analysis; D041623:Tomography, Optical Coherence; D055815:Young Adult
keywords: Bowman's layer; aging; collagen; image analysis; in vivo confocal microscopy