title: An accurate method to determine Bowman's layer thickness in vivo in the human cornea.
abstract: OBJECTIVE
  To determine an accurate value for Bowman's layer (BL) thickness in vivo in humans.
  
  
  METHODS
  Seventeen corneal transplant patients were examined preoperatively by laser-scanning in vivo confocal microscopy (IVCM), and corneal buttons were removed postoperatively and sectioned for light microscopy (LM). Nine corneas with uniformly thick BL by LM were used for thickness measurement. In the uniformly thick samples, probable overestimation of BL thickness in vivo by a first in vivo method (Method 1) led to the development of a revised in vivo method (Method 2). Method 2 was used to measure BL thickness in 20 healthy volunteers.
  
  
  RESULTS
  In nine patients, mean BL thickness prior to transplantation was 13.7 ± 1.6 μm by IVCM (Method 1) while BL thickness of the removed corneal button was 9.7 ± 1.7 μm by LM (P < 0.001). The correlation of BL thickness between IVCM (Method 1) and LM was poor (P = 0.226). In 20 right eyes of 20 normal corneas, both in vivo methods were used to determine BL thickness. Mean BL thickness by Method 1 was 13.2 ± 1.6 μm and by Method 2 was 9.1 ± 1.4 μm (P < 0.001). BL thickness measurements by both in vivo methods were highly correlated (P < 0.001).
  
  
  CONCLUSIONS
  BL thickness by a revised in vivo method was close to LM values in this study and to values reported in fixed tissue in other studies. The authors believe this revised method provides the most accurate estimates of BL thickness in vivo to date.
authors.affiliation: Division of Ophthalmology, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Germundsson
authors.forename: Per
authors.initials: P
authors.lastname: Fagerholm
authors.forename: Marina
authors.initials: M
authors.lastname: Koulikovska
authors.forename: Neil S
authors.initials: NS
authors.lastname: Lagali
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D050541:Bowman Membrane / Q000473:pathology*; D016022:Case-Control Studies; D016039:Corneal Transplantation; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D008859:Microscopy, Polarization; D008875:Middle Aged; D055815:Young Adult