title: Axial length's role in intraocular lens power calculation error in X-linked megalocornea: a case-series analysis.
abstract: OBJECTIVE
  To retrospectively analyze the potential sources of error for IOL power calculation in patients with X-linked related megalocornea (XLMC).
  
  
  METHODS
  Case report and comparative analysis of refractive outcomes in previously reported phacoemulsification procedures in XLMC cases.
  
  
  RESULTS
  A 52-year-old patient with XLMC and cataracts underwent bilateral clear corneal phacoemulsification, capsule tension ring (CTR) insertion, and in the bag intraocular lens (IOL) implantation. Two years after the procedure the IOL remained centrally located and stable in both eyes. In the postoperative refraction, the patient had a large hyperopic refractive error in the right eye, and a moderate hyperopic refractive error in the left eye. A similar pattern was observed in previously reported cases. Pooling all cases together we observed that the Holladay II formula produced more accurate IOL power calculations than the SRK-T formula. Still, both formulas diverged from the ideal IOL power by approximately 1 diopter per mm of axial length in subjects with axial lengths larger than 24 mm.
  
  
  CONCLUSIONS
  Axial length seems to be the main source of IOL power calculation error in XLMC patients. Compared to SRK-T the Holladay II formula provides better refractive results, yet both formulas may require further adjustment depending on the axial length.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Division of Cornea and External Disease, WK Kellogg Eye Center, University of Michigan Medical School , Ann Arbor, MI , USA .
authors.forename: Paola
authors.initials: P
authors.lastname: De la Parra-Colín
authors.forename: Tonatiuh
authors.initials: T
authors.lastname: Barrientos-Gutierrez
authors.forename: Shahzad I
authors.initials: SI
authors.lastname: Mian
mesh_terms: D000465:Algorithms; D058452:Axial Length, Eye / Q000473:pathology*; D002386:Cataract / Q000150:complications*; D015785:Eye Diseases, Hereditary / Q000150:complications*; D040181:Genetic Diseases, X-Linked / Q000150:complications*; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D055095:Optics and Photonics; D018918:Phacoemulsification; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology
keywords: Intraocular lens calculation; X-linked megalocornea; refractive error