title: Logarithmic transformation of spectral-domain optical coherence tomography data in uveitis-associated macular edema.
abstract: OBJECTIVE
  To determine the utility of logarithmic transformation of spectral-domain optical coherence tomography (logSD-OCT) retinal thickness data for assessment of clinically meaningful changes in uveitis-associated macular edema.
  
  
  METHODS
  Patients with noninfectious uveitis-associated macular edema at our institution between August 2010 and March 2011 were identified. Only those with SD-OCT imaging were included. The clinical diagnoses, visual acuities, and central subfield thickness (CST) measurements were recorded. Logarithmic transformation of the retinal thickness was performed and frequency histograms plotted. A linear mixed-effects model of the logarithm minimum angle of resolution (logMAR) visual acuity on logSD-OCT was created to account for within-patient correlation among visits and between eyes.
  
  
  RESULTS
  A total of 98 SD-OCT images from 34 patients were analyzed. The mean age at examination was 40 years (range, 11-69 years). Anatomic diagnoses included anterior/intermediate uveitis (23%), intermediate uveitis (21%), posterior uveitis (12%), and panuveitis (44%). LogSD-OCT data provided a more normal distribution than standard CST. Skewness and kurtosis of CST data were 1.04 and 0.37, respectively, and skewness and kurtosis of logSD-OCT data were 0.40 and -0.48, respectively. There was a positive correlation between logSD-OCT and logMAR visual acuity. Specifically, for each 0.1-unit increase in logSD-OCT, the logMAR visual acuities increased (worsened) by 0.082 units (95% CI: 0.057-0.107, P < 0.001).
  
  
  CONCLUSIONS
  Logarithmic transformation of SD-OCT measurements provided a more normal distribution and positively correlated with logMAR visual acuity. This transformation of retinal thickness may be valuable for assessing clinically significant changes in SD-OCT measurements in future uveitis studies.
authors.affiliation: Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Payne
authors.forename: Beau B
authors.initials: BB
authors.lastname: Bruce
authors.forename: Lyndon B K
authors.initials: LB
authors.lastname: Lee
authors.forename: Steven
authors.initials: S
authors.lastname: Yeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006801:Humans; D016015:Logistic Models; D008266:Macula Lutea / Q000473:pathology*; D008269:Macular Edema / Q000209:etiology / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*; D014605:Uveitis / Q000150:complications / Q000473:pathology*; D014792:Visual Acuity; D055815:Young Adult