title: Reduction in corneal volume with severity of keratoconus.
abstract: OBJECTIVE
  To compare the corneal volume in keratoconic and normal eyes to improve our understanding of the tissue distribution associated with the disease.
  
  
  METHODS
  The Oculus Pentacam tomographer (Oculus Inc., Wetzlar, Germany) was used to analyze the corneal volume contained within discs with diameters of 3, 5, 7, and 10 mm in 21 patients with keratoconus and 21 matched healthy control subjects.
  
  
  RESULTS
  Corneal volume was significantly decreased in the keratoconus group (keratoconus vs. control group: 3.44 ± 0.39 vs. 4.05 ± 0.29 mm(3), 10.34 ± 0.95 vs. 11.79 ± 0.84 mm(3), 22.80 ± 1.73 vs. 25.26 ± 1.74 mm(3), and 57.17 ± 3.94 vs. 61.90 ± 4.12 mm(3) for the 3-, 5-, 7-, and 10-mm diameter discs, respectively; p < 0.001). As the corneal disc diameter analyzed increased, fewer differences were found between the control corneas and keratoconic corneas at different stages of the disease. Within the 3-mm and 5-mm diameter discs, significant differences were detected between the control group, moderate keratoconus, and the severe keratoconus groups (p < 0.05). However, within the 10-mm discs, differences were only detected between the control group and the severe keratoconus group (p = 0.005).
  
  
  CONCLUSIONS
  Corneal volume was significantly decreased in keratoconus, particularly in the central and paracentral area. The decrease in corneal volume in moderate and severe keratoconus as detected by the Pentacam tomographer, may be explained by loss of corneal tissue. In the early stages of the disease, the altered metabolic activity may cause tissue stretching and, as the disease progresses, this stretching is then accompanied by tissue loss.
authors.affiliation: Department of Optometry, Dublin Institute of Technology, Dublin, Ireland.
authors.forename: Luisa Simo
authors.initials: LS
authors.lastname: Mannion
authors.forename: Cindy
authors.initials: C
authors.lastname: Tromans
authors.forename: Clare
authors.initials: C
authors.lastname: O'Donnell
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D007640:Keratoconus / Q000473:pathology*; D008297:Male; D009929:Organ Size; D011446:Prospective Studies; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence / Q000379:methods*