title: Highly precise eye length measurements in children aged 3 through 12 years.
abstract: OBJECTIVE
  To determine the feasibility, reliability, and validity of using partial coherence interferometry, a noncontact method that detects interference patterns from various layers of the eye, to measure axial length in young children.
  
  
  METHODS
  The right eye of 64 subjects (mean age, 8.4 y; age range, 3.4-12.9 y; best-corrected visual acuity >or=20/30) was measured. Subjects fixated monocularly on the collimated light pattern from a laser diode (the alignment beam) and the operator used a video monitor to align the corneal reflection in the optical path. Axial length was measured during an 0.8-second scan using interference patterns from a collimated short coherence superluminescence diode aligned coaxially with the laser diode. Five series of 16 readings each were obtained. The average axial length for each of the 5 series of readings was calculated. Main Outcome Measure Axial length.
  
  
  RESULTS
  Within-subject precision of axial length measurements was high, with an overall SE of measurement of 8 micro m for individual subjects across the 5 sessions (95% confidence interval, +/-16 micro m). Subgroup analysis showed that sex, age, spherical equivalent, and refractive error exerted statistically significant effects on precision, but all of the differences among subgroups were 3 micro m or less and likely to be insignificant clinically. Axial length measured by partial coherence interferometry varied systematically, with factors known to influence eye length (ie, age and refractive error), further validating the measurement method.
  
  
  CONCLUSIONS
  The partial coherence interferometry technique provides reproducible, extraordinarily precise eye length measurements in young children and should enable novel approaches to study eye growth and refractive development.
authors.affiliation: Division of Pediatric Ophthalmology, The Children's Hospital of Philadelphia, One Children's Center, PA 19104, USA.
authors.forename: Graham E
authors.initials: GE
authors.lastname: Quinn
authors.forename: Ellie L
authors.initials: EL
authors.lastname: Francis
authors.forename: Karen S
authors.initials: KS
authors.lastname: Nipper
authors.forename: D Ian
authors.initials: DI
authors.lastname: Flitcroft
authors.forename: Gui-shuang
authors.initials: GS
authors.lastname: Ying
authors.forename: Renee C
authors.initials: RC
authors.lastname: Rees
authors.forename: Gregor F
authors.initials: GF
authors.lastname: Schmid
authors.forename: Maureen G
authors.initials: MG
authors.lastname: Maguire
authors.forename: Richard A
authors.initials: RA
authors.lastname: Stone
mesh_terms: D001837:Body Weights and Measures; D002648:Child; D002675:Child, Preschool; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005123:Eye / Q000033:anatomy & histology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007368:Interferometry / Q000379:methods; D008027:Light; D008297:Male; D015203:Reproducibility of Results; D014792:Visual Acuity