title: Topographic variation of choroidal and retinal thicknesses at the macula in healthy adults.
abstract: OBJECTIVE
  To determine the topographic variation of macular choroidal and retinal thicknesses (RTs) in normal eyes and their relationship with refractive error.
  
  
  METHODS
  Spectral domain optical coherence tomography with enhanced depth imaging was performed on 124 healthy participants using a standardised imaging protocol. Manual segmentation of choroidal boundaries was performed by trained graders, and mean choroidal thickness (CT) was compared with mean RT in corresponding sectors of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid.
  
  
  RESULTS
  Mean central subfield CT was 322.2 µm. The choroid was thickest at the temporal and superior sectors (323.1-338.1 µm), followed by inferior sectors (314.0-321.8 µm), and thinnest at the nasal sectors (232.8-287.8 µm). In contrast, the retina was thicker nasally (343.4 µm) and thinner temporally (287.1 µm). CT was thickest among emmetropes in all ETDRS subfields and became thinner progressively among low, moderate and high myopes (p<0.001). The variation of both choroidal and RTs among refractive error groups resulted in different topographic patterns at the macula.
  
  
  CONCLUSIONS
  There is significant topographic variation of choroidal and RTs at different regions of the macula, with progressive change of choroidal thickness in all sectors based on the refractive status of the eye.
authors.affiliation: National Healthcare Group Eye Institute, Tan Tock Seng Hospital, , Singapore, Singapore.
authors.forename: Colin S H
authors.initials: CS
authors.lastname: Tan
authors.forename: Kai Xiong
authors.initials: KX
authors.lastname: Cheong
authors.forename: Louis W
authors.initials: LW
authors.lastname: Lim
authors.forename: Kelvin Z
authors.initials: KZ
authors.lastname: Li
mesh_terms: D000328:Adult; D044466:Asian People / Q000208:ethnology; D002681:China / Q000453:epidemiology; D002829:Choroid / Q000033:anatomy & histology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009929:Organ Size; D012030:Refractive Errors / Q000175:diagnosis; D012160:Retina / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence; D055815:Young Adult
keywords: Choroid; Imaging; Macula; Retina; Vision