title: Vertical D: a novel topographic pattern in some keratoconus suspects.
abstract: OBJECTIVE
  To describe a novel topographic curvature pattern, vertical D, which was present in some keratoconus suspects. This pattern was detected retrospectively in 2 patients who developed post-LASIK ectasia and prospectively in 4 patients who had other corneal abnormalities suggestive of keratoconus.
  
  
  METHODS
  Retrospective interventional case series and prospective cross-sectional study.
  
  
  METHODS
  After vertical D topographic curvature patterns were noted in 2 patients (3 eyes) who developed post-LASIK ectasia, 1168 consecutive potential refractive surgical candidates (2336 eyes) evaluated at a refractive center were screened to detect this vertical D pattern.
  
  
  METHODS
  Placido disc-based curvature topography, ultrasound pachymetry, and elevation-based Scheimpflug topography were performed on these patients.
  
  
  METHODS
  Corneal curvature topographic patterns, central keratometry, inferior-superior and nasal-temporal ratios, skewed radial axis value, Humphrey Atlas PathFinder corneal analysis, corneal thickness, and corneal anterior and posterior elevation.
  
  
  RESULTS
  Four additional patients (7 eyes) with vertical D patterns were found (prevalence, 0.34%). In addition to this vertical D pattern, these patients had central corneal thickness < 500 microm and/or posterior corneal protrusion > 20 microm or positive results on keratoconus detection analyses. The 10 eyes with the vertical D pattern had more horizontal (nasal-temporal ratio) than vertical (inferior-superior ratio) curvature asymmetry: 0.98+/-0.04 diopters versus 0.44+/-0.2 diopters (paired t test, P<0.001).
  
  
  CONCLUSIONS
  We propose that vertical D is a novel corneal curvature pattern reflecting horizontal asymmetry that was present in keratoconus suspect patients even if standard keratoconus analyses' results were negative.
authors.affiliation: Laser Eye Center of Miami, Miami, Florida, USA. jcabad@gmail.com
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Abad
authors.forename: Roy S
authors.initials: RS
authors.lastname: Rubinfeld
authors.forename: Maria
authors.initials: M
authors.lastname: Del Valle
authors.forename: Michael W
authors.initials: MW
authors.lastname: Belin
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Kurstin
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D004108:Dilatation, Pathologic / Q000209:etiology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D012189:Retrospective Studies