title: Macular thickness measurements using Copernicus Spectral Domain Optical Coherence Tomography.
abstract: OBJECTIVE
  To provide normal macular thickness measurements using Spectral Domain Optical Coherence Tomography (SDOCT, Copernicus, Optopol Technologies, Zawierci, Poland).
  
  
  METHODS
  Fifty-eight eyes of 58 healthy subjects were included in this prospective study. All subjects had comprehensive ophthalmic examination including best-corrected visual acuity (BCVA). All the subjects underwent Copernicus SDOCT. Central foveal thickness (CFT) and photoreceptor layer (PRL) thickness were measured and expressed as mean and standard deviation. Mean retinal thickness for each of the 9 regions defined in the Early Treatment Diabetic Retinopathy Study was reported. The data were compared with published literature in Indians using Stratus and Spectralis OCTs to assess variation in instrument measurements.
  
  
  RESULTS
  The mean CFT in the study sample was 173.8 ± 18.16 microns (131-215 microns) and the mean PRL thickness was 65.48 ± 4.23 microns (56-74 microns). No significant difference (p = 0.148) was found between CFT measured automated (179.28 ± 22 microns) and manually (173.83 ± 18.1 microns). CFT was significantly lower in women (167.62 ± 16.36 microns) compared to men (180.03 ± 18 microns) (p = 0.008). Mean retinal thickness reported in this study was significantly different from published literature using Stratus OCT and Spectralis OCT.
  
  
  CONCLUSIONS
  We report the normal mean retinal thickness in central 1 mm area to be between 138 and 242 microns in Indian population using Copernicus SDOCT. We suggest that different OCT instruments cannot be used interchangeably for the measurement of macular thickness as they vary in segmentation algorithms.
authors.affiliation: Elite School of Optometry, No. 8, G.S.T. Road, St. Thomas Mount, Chennai 600 016, Tamil Nadu, India ; Birla Institute of Technology and Science, Pilani, India.
authors.forename: Laxmi
authors.initials: L
authors.lastname: Gella
authors.affiliation: Shri Bhagwan Mahavir Vitreoretinal Services, 18, College Road, Sankara Nethralaya, Chennai 600 006, Tamil Nadu, India.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Raman
authors.affiliation: Shri Bhagwan Mahavir Vitreoretinal Services, 18, College Road, Sankara Nethralaya, Chennai 600 006, Tamil Nadu, India.
authors.forename: Tarun
authors.initials: T
authors.lastname: Sharma
keywords: Foveal thickness; Photoreceptor layer thickness; Retina; Retinal thickness; Spectral Domain Optical Coherence Tomography