title: The endothelial sample size analysis in corneal specular microscopy clinical examinations.
abstract: OBJECTIVE
  To evaluate endothelial cell sample size and statistical error in corneal specular microscopy (CSM) examinations.
  
  
  METHODS
  One hundred twenty examinations were conducted with 4 types of corneal specular microscopes: 30 with each BioOptics, CSO, Konan, and Topcon corneal specular microscopes. All endothelial image data were analyzed by respective instrument software and also by the Cells Analyzer software with a method developed in our lab. A reliability degree (RD) of 95% and a relative error (RE) of 0.05 were used as cut-off values to analyze images of the counted endothelial cells called samples. The sample size mean was the number of cells evaluated on the images obtained with each device. Only examinations with RE < 0.05 were considered statistically correct and suitable for comparisons with future examinations. The Cells Analyzer software was used to calculate the RE and customized sample size for all examinations.
  
  
  RESULTS
  Bio-Optics: sample size, 97 ± 22 cells; RE, 6.52 ± 0.86; only 10% of the examinations had sufficient endothelial cell quantity (RE < 0.05); customized sample size, 162 ± 34 cells. CSO: sample size, 110 ± 20 cells; RE, 5.98 ± 0.98; only 16.6% of the examinations had sufficient endothelial cell quantity (RE < 0.05); customized sample size, 157 ± 45 cells. Konan: sample size, 80 ± 27 cells; RE, 10.6 ± 3.67; none of the examinations had sufficient endothelial cell quantity (RE > 0.05); customized sample size, 336 ± 131 cells. Topcon: sample size, 87 ± 17 cells; RE, 10.1 ± 2.52; none of the examinations had sufficient endothelial cell quantity (RE > 0.05); customized sample size, 382 ± 159 cells.
  
  
  CONCLUSIONS
  A very high number of CSM examinations had sample errors based on Cells Analyzer software. The endothelial sample size (examinations) needs to include more cells to be reliable and reproducible. The Cells Analyzer tutorial routine will be useful for CSM examination reliability and reproducibility.
authors.affiliation: Department of Ophthalmology of Erast Gaertner Hospital and Federal University of Paraná, Curitiba, Brazil. drfcabib@mps.com.br
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Abib
authors.forename: Ricardo
authors.initials: R
authors.lastname: Holzchuh
authors.forename: Artur
authors.initials: A
authors.lastname: Schaefer
authors.forename: Tania
authors.initials: T
authors.lastname: Schaefer
authors.forename: Ronialci
authors.initials: R
authors.lastname: Godois
mesh_terms: D000328:Adult; D002452:Cell Count; D004728:Endothelium, Corneal / Q000166:cytology*; D006801:Humans; D008853:Microscopy; D008875:Middle Aged; D018401:Sample Size; D015983:Selection Bias