title: Which soft contact lens power is better for piggyback fitting in keratoconus?
abstract: OBJECTIVE
  To evaluate the impact of differente soft contact lens power in the anterior corneal curvature and regularity in subjects with keratoconus.
  
  
  METHODS
  Nineteen subjects (30 eyes) with keratoconus were included in the study. Six corneal topographies were taken with Pentacam Eye System over the naked eye and successively with soft lens (Senofilcon A) powers of -3.00, -1.50, 0.00, +1.50 and +3.00 D. Corneal measurements of mean central keratometry (MCK), maximum tangential curvature (TK), maximum front elevation (MFE) and eccentricity (Ecc) at 6 and 8 mm diameters as well as anterior corneal surface high order aberrations (i.e. total RMS, spherical- and coma-like and secondary astigmatism) were evaluated.
  
  
  RESULTS
  Negative- and plano-powered soft lenses flattened (p<0.05 in all cases), whereas positive-powered lenses did not induce any significant changes (p>0.05 in all cases) in MCK in comparison to the naked eye. The TK power decreased with negative lenses (p<0.05 in both cases) and increased with +3.00 D lenses (p=0.03) in comparison to the naked eye. No statistically significant differences were found in MFE with any soft lens power in comparison to the naked eye (p>0.05 in all cases). Corneal eccentricity increased at 8 mm diameter for all lens powers (p<0.05 in all cases). No statistically differences were found in HOA RMS and spherical-like aberration (both p>0.05). Statistically differences were found in coma-like and secondary astigmatism (both p<0.05).
  
  
  CONCLUSIONS
  Negative-powered soft contact lenses provide a flatter anterior surface in comparison to positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting.
authors.affiliation: MGR Doctores, Madrid, Spain. mrjlentes@gmail.com
authors.forename: Miguel
authors.initials: M
authors.lastname: Romero-Jiménez
authors.forename: Jacinto
authors.initials: J
authors.lastname: Santodomingo-Rubido
authors.forename: Patricia
authors.initials: P
authors.lastname: Flores-Rodríguez
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: González-Méijome
mesh_terms: D000293:Adolescent; D000328:Adult; D003263:Contact Lenses, Hydrophilic; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D004867:Equipment Design; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis / Q000628:therapy*; D008297:Male; D012720:Severity of Illness Index; D014792:Visual Acuity; D055815:Young Adult