title: Choroidal thickness measurement in myopic eyes by enhanced depth optical coherence tomography.
abstract: OBJECTIVE
  To measure choroidal thickness (CT) in myopic eyes using enhanced depth imaging (EDI).
  
  
  METHODS
  A cross-sectional study.
  
  
  METHODS
  Fifty-six consecutive patients with spherical equivalent refractive error of at least 6 diopters (D) were evaluated.
  
  
  METHODS
  Enhanced depth imaging optical coherence tomography (OCT) images were obtained by positioning the spectral-domain OCT device close enough to the eye to acquire an enhanced signal of the choroidal layer. Choroidal depth was measured as the distance between the outer reflective retinal pigment epithelium (RPE) layer and the inner sclera border. Measurements were made in a horizontal fashion across the fovea at 500-μm intervals of the sections. The CT was measured at the subfoveal region in a horizontal fashion, 3 mm temporal to fovea and 3 mm nasal to fovea.
  
  
  METHODS
  Correlations among CT with age, refractive error in diopters, and visual acuity in logarithm of the minimum angle of resolution (logMAR) were analyzed with linear mixed models.
  
  
  RESULTS
  The mean age of the 56 patients was 50.4 years (± 2.03 years standard deviation; interquartile range [IQR], 42-62 years), and the mean refractive error was -8.7 D (IQR, -6.1 to -11 D). The mean subfoveal CT was 118 μm (± 68 μm) and correlated negatively with age (P = 0.032) and refractive error (P = 0.011). Regression analysis suggested that subfoveal CT decreased by 11.9 μm for each decade of life and by 6.205 μm for each diopter of myopia. The subfoveal CT was inversely correlated with the logMAR visual acuity (P = 0.008), and visual acuity improved by 0.02 (logMAR) in a 10-μm increase in CT.
  
  
  CONCLUSIONS
  Choroidal thickness decreases with age and severity of myopia. Visual acuity decreases in line with decreasing subfoveal CT. A reduction in CT is related to aging and the severity of myopia, whereas visual acuity depends on subfoveal CT. Our study supports the theory that choroidal abnormality may play a key role in the pathogenesis of myopic degeneration.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Department of Ophthalmology & Visual Sciences, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong.
authors.forename: Mary
authors.initials: M
authors.lastname: Ho
authors.forename: David T L
authors.initials: DT
authors.lastname: Liu
authors.forename: Vesta C K
authors.initials: VC
authors.lastname: Chan
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002829:Choroid / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis*; D009929:Organ Size; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult