title: Quantitative analysis of collagen lamellae in the normal and keratoconic human cornea by second harmonic generation imaging microscopy.
abstract: OBJECTIVE
  To characterize the structural properties of collagen lamellae in the normal and keratoconic human corneal stroma, we measured their width and angle relative to Bowman's layer (BL).
  
  
  METHODS
  Thirteen normal and four keratoconic corneas were examined. Collagen lamellae in tissue blocks from the central cornea were visualized by second harmonic generation imaging microscopy. Images obtained in 1-μm steps from BL to Descemet's membrane (DM) were subjected to three-dimensional reconstruction. The reconstructed data sets were divided into 10 layers of equal depth (L1-L10) for analysis. The width of lamellae adherent to BL (L0) was also determined.
  
  
  RESULTS
  For the normal cornea, the width (mean ± SD) of collagen lamellae was 6.5 ± 1.7 μm at L0, decreased to 4.3 ± 1.3 μm at L1, and then increased gradually with progression toward DM to 122.2 ± 34.5 μm at L10, whereas the angle of lamellae was 20.9° ± 5.4° at L1 and decreased initially to 10.6° ± 3.2° at L2 before declining gradually to 2.7° ± 2.2° at L10. The width and angle of collagen lamellae in the keratoconic cornea were significantly larger and smaller, respectively, relative to those in the normal cornea.
  
  
  CONCLUSIONS
  In the normal human cornea, collagen lamellae adjacent to BL are narrow and form a steep angle with BL, whereas they increase in width and their angle relative to BL flattens with progression toward DM. These properties of collagen lamellae are altered in keratoconus and are likely related to abnormalities of corneal shape.
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Morishige
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Shin-Gyou-Uchi
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Haruya
authors.initials: H
authors.lastname: Azumi
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ohta
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Morita
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kimura
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka, Fukuoka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takahara
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Koh-Hei
authors.initials: KH
authors.lastname: Sonoda
mesh_terms: D000328:Adult; D003094:Collagen / Q000032:analysis*; D003319:Corneal Stroma / Q000737:chemistry / Q000473:pathology*; D003952:Diagnostic Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007640:Keratoconus / Q000175:diagnosis* / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods*; D008875:Middle Aged; D015203:Reproducibility of Results
chemical_list: D003094:Collagen
keywords: collagen; corneal stroma; keratoconus; normal cornea; second harmonic generation