title: The role of preoperative biometry in selecting initial contact lens power in the Infant Aphakia Treatment Study.
abstract: OBJECTIVE
  To investigate the role of preoperative biometry for selecting initial contact lens power.
  
  
  METHODS
  Patients randomized to receive contact lenses in the Infant Aphakia Treatment Study (IATS) were retrospectively analyzed. Inclusion criteria were availability of both a preoperative immersion axial length measurement and a 1-month postoperative refractive value. The target contact lens power for distance was determined using 1-month postoperative spherical equivalent refraction (after adjusting for a vertex distance) over the known contact lens power. We compared targeted contact lens power for distance with three other treatment techniques: (1) 30 D contact lens (32 D minus 2 D overcorrection for near vision based on IATS protocol); (2) regression-estimated contact lens power of 84.4 - 3.2 × axial length; and (3) IOL power calculated using the Sanders-Retzlaff-Kraff (SRK/T) regression formula with a modified A-constant (112.176). Prediction error (targeted minus estimated contact lens power) and its absolute values were calculated.
  
  
  RESULTS
  A total of 34 eyes of 34 patients met inclusion criteria. Age at the time of cataract surgery was 2.4 ± 1.7 months. Follow-up refraction was performed at 31 ± 3 days after surgery. Target contact lens power for distance was 26.0 ± 4.5 D for the IATS cohort (which excluded infants with corneal diameter <9 mm). The mean prediction error was -4.0, -1.0, and -2.0 D and mean absolute prediction error was 4.4, 2.2, and 2.9 D, respectively, for 30 D contact lens, regression, and SRK/T-estimated power.
  
  
  CONCLUSIONS
  Preoperative biometry can be used to estimate contact lens power for distance if an accurate refraction cannot be obtained initially.
authors.affiliation: Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina. Electronic address: trivedi@musc.edu.
authors.forename: Rupal H
authors.initials: RH
authors.lastname: Trivedi
authors.affiliation: Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Lambert
authors.affiliation: Department of Biostatistics and Bioinformatics, School of Public Health, Emory University, Atlanta, Georgia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynn
authors.affiliation: Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: M Edward
authors.initials: ME
authors.lastname: Wilson
mesh_terms: D001036:Aphakia, Postcataract / Q000628:therapy*; D058452:Axial Length, Eye / Q000473:pathology; D001699:Biometry / Q000379:methods; D002386:Cataract / Q000151:congenital*; D002387:Cataract Extraction; D003261:Contact Lenses; D005260:Female; D006801:Humans; D007223:Infant; D019654:Lens Implantation, Intraocular; D008297:Male; D055095:Optics and Photonics; D057234:Preoperative Period; D017755:Prosthesis Fitting; D012030:Refractive Errors / Q000175:diagnosis; D042262:Retinoscopy; D012189:Retrospective Studies