title: Estimation of ocular volume from axial length.
abstract: OBJECTIVE
  To determine which biometric parameters provide optimum predictive power for ocular volume.
  
  
  METHODS
  Sixty-seven adult subjects were scanned with a Siemens 3-T MRI scanner. Mean spherical error (MSE) (D) was measured with a Shin-Nippon autorefractor and a Zeiss IOLMaster used to measure (mm) axial length (AL), anterior chamber depth (ACD) and corneal radius (CR). Total ocular volume (TOV) was calculated from T2-weighted MRIs (voxel size 1.0 mm(3)) using an automatic voxel counting and shading algorithm. Each MR slice was subsequently edited manually in the axial, sagittal and coronal plane, the latter enabling location of the posterior pole of the crystalline lens and partitioning of TOV into anterior (AV) and posterior volume (PV) regions.
  
  
  RESULTS
  Mean values (±SD) for MSE (D), AL (mm), ACD (mm) and CR (mm) were -2.62±3.83, 24.51±1.47, 3.55±0.34 and 7.75±0.28, respectively. Mean values (±SD) for TOV, AV and PV (mm(3)) were 8168.21±1141.86, 1099.40±139.24 and 7068.82±1134.05, respectively. TOV showed significant correlation with MSE, AL, PV (all p<0.001), CR (p=0.043) and ACD (p=0.024). Bar CR, the correlations were shown to be wholly attributable to variation in PV. Multiple linear regression indicated that the combination of AL and CR provided optimum R(2) values of 79.4% for TOV.
  
  
  CONCLUSIONS
  Clinically useful estimations of ocular volume can be obtained from measurement of AL and CR.
authors.affiliation: School of Life & Health Sciences, Aston University, Birmingham, UK.
authors.forename: Manbir
authors.identifier: http://orcid.org/0000-0002-7991-5881
authors.initials: M
authors.lastname: Nagra
authors.affiliation: School of Life & Health Sciences, Aston University, Birmingham, UK.
authors.forename: Bernard
authors.initials: B
authors.lastname: Gilmartin
authors.affiliation: School of Life & Health Sciences, Aston University, Birmingham, UK.
authors.forename: Nicola S
authors.initials: NS
authors.lastname: Logan
mesh_terms: D000293:Adolescent; D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology; D058452:Axial Length, Eye / Q000033:anatomy & histology*; D001699:Biometry; D003315:Cornea / Q000033:anatomy & histology; D005123:Eye / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007368:Interferometry; D008279:Magnetic Resonance Imaging; D008297:Male; D009929:Organ Size; D012029:Refraction, Ocular / Q000502:physiology; D055815:Young Adult
keywords: Eye (Globe); Imaging; Optics and Refraction