title: Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics.
abstract: OBJECTIVE
  To evaluate the clinical features of keratoconus taking into consideration anterior corneal aberrations, internal astigmatism, and corneal biomechanical properties and to define a new grading system based on visual limitation.
  
  
  METHODS
  Vissum Corporation, Alicante, Spain.
  
  
  METHODS
  Retrospective case series.
  
  
  METHODS
  This multicenter study comprised consecutive keratoconic eyes with no previous ocular surgery or active ocular disease. Visual, refractive, corneal topography, and pachymetry outcomes were analyzed. Internal astigmatism was calculated by vectorial analysis. Corneal aberrations and corneal biomechanics characterized by the Ocular Response Analyzer were evaluated in some eyes. Correlations between clinical data and a linear multiple regression analysis for characterizing the relationship between visual limitation and objective clinical data were performed.
  
  
  RESULTS
  This study comprised 776 eyes of 507 patients (age range 11 to 79 years) The mean keratometry (K) correlated significantly with logMAR corrected distance visual acuity (CDVA) (r = 0.591, P<.01), internal astigmatism (r = 0.497, P<.01), corneal asphericity (r = -0.647, P<.01), and several corneal higher-order aberrometric coefficients (r≥0.603, P<.01). Significant correlations were found between some corneal aberrometric parameters and CDVA (r≥0.444, P<.01). Multiple regression analysis showed that CDVA was significantly correlated with the mean K, intraocular pressure, corneal resistance factor, and spherical equivalent (r(2) = 0.69, P<.01). There were significant differences in mean K, internal astigmatism, and corneal higher-order aberrations between 4 groups differentiated by visual limitation (P<.01).
  
  
  CONCLUSIONS
  The visual limitation in keratoconus could be explained by different alterations that occur in these corneas and allowed development of a new grading system for this condition.
authors.affiliation: Keratoconus Unit, Vissum Corporation-Instituto Oftalmológico de Alicante, Alicante, Spain.
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
authors.forename: David P
authors.initials: DP
authors.lastname: Piñero
authors.forename: Alicia
authors.initials: A
authors.lastname: Alesón
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Teus
authors.forename: Rafael I
authors.initials: RI
authors.lastname: Barraquer
authors.forename: Joaquim
authors.initials: J
authors.lastname: Murta
authors.forename: Miguel J
authors.initials: MJ
authors.lastname: Maldonado
authors.forename: Gracia
authors.initials: G
authors.lastname: Castro de Luna
authors.forename: Ramón
authors.initials: R
authors.lastname: Gutiérrez
authors.forename: César
authors.initials: C
authors.lastname: Villa
authors.forename: Antonio
authors.initials: A
authors.lastname: Uceda-Montanes
mesh_terms: D057128:Aberrometry; D000293:Adolescent; D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000503:physiopathology*; D001696:Biomechanical Phenomena / Q000502:physiology*; D002648:Child; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D057108:Corneal Wavefront Aberration / Q000503:physiopathology*; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology