title: Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus.
abstract: OBJECTIVE
  To evaluate the corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and clinical keratoconus.
  
  
  METHODS
  Vissum Corporation, Alicante, Spain.
  
  
  METHODS
  Eyes were placed into 1 of 4 groups as follows: keratoconus 2 (grade II), keratoconus 1 (grade I), subclinical (subclinical keratoconus), and control (normal eyes). All eyes had an ophthalmologic examination including corneal evaluation (curvature, elevation, asphericity, pachymetry, corneal volume) by rotating Scheimpflug imaging (Pentacam). The posterior-anterior corneal power ratio was also calculated.
  
  
  RESULTS
  Seventy-one eyes (51 patients; aged 16 to 64 years) were evaluated. Astigmatism and keratometry of both corneal surfaces were statistically significantly higher in the keratoconus 1 and 2 groups (P<or=.02). Posterior astigmatism was statistically significantly higher in the subclinical group than in the control group (P = .01). A strong correlation (r>or=-0.81) was found between anterior and posterior curvature in the normal and subclinical groups; the correlation was weaker in clinical keratoconus cases (r<or=-0.56). The correlation in astigmatism between the anterior and posterior surface was good in all keratoconus groups (r>or=0.81). The posterior-anterior corneal power ratio was significantly higher in the keratoconus 2 group than in the other groups (P<or=.01). Pachymetric readings were progressively lower in eyes with subclinical, early, or moderate keratoconus (P<.01). The corneal volume was statistically significantly lower in the keratoconus 2 group than in the other groups (P = .04).
  
  
  CONCLUSIONS
  The correlation between anterior and posterior corneal curvature was lower in keratoconus, although the correlation between anterior and posterior astigmatism was maintained.
authors.affiliation: Keratoconus Unit, Vissum Corporation-Instituto Oftalmologico de Alicante, Departamento de Optica, Universidad de Alicante, Alicante, Spain. dpinero@vissum.com
authors.forename: David P
authors.initials: DP
authors.lastname: Piñero
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
authors.forename: Alicia
authors.initials: A
authors.lastname: Alesón
authors.forename: Munir
authors.initials: M
authors.lastname: Escaf Vergara
authors.forename: Mauricio
authors.initials: M
authors.lastname: Miranda
mesh_terms: D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D001251:Astigmatism / Q000175:diagnosis; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D004728:Endothelium, Corneal / Q000473:pathology; D019573:Epithelium, Corneal / Q000473:pathology; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007640:Keratoconus / Q000145:classification* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology