Importance of standardizing the number of cells measured for coefficient of variation (COV) estimates of corneal endothelial cell area values as relevant to contact lens wear.

Contact Lens & Anterior Eye : the Journal of the British Contact Lens Association
Michael J Doughty

Abstract

To assess the impact of using different numbers of cells in calculations of the coefficient of variation (COV) value for normal and polymegethous endothelia METHODS: Four sets of 20 non-contact specular microscope images obtained from Caucasian individuals were assessed, and categorized according to the extent of polymegethism, i.e. grade 0 (none), grade 1 (mild), grade 2 (moderate) and grade 3 (substantial). Cell areas were measured manually and then values for between 2 and 100 cells were progressively added and averaged to generate COV estimates. These were then assessed in terms of their relative values (as percentages +/- SD) in relation to the value obtained on over 100 cells. For the 4 sets of endothelia with group-mean COV values of 25.8, 33.1, 45.1 and 56.8%, the reliability of the COV estimates realized asymptotic values of close to ±1.0, ±2.7, ±3.6 and ±5.0% with 90 cells, but with greater uncertainty with few numbers of cells, e.g. only to within ±3.4, ±5.3, ±6.1 and ±7.9% with 75 cells. COV estimates for the corneal endothelium are dependent on the number of cells used in the calculations. It is recommended that every effort should be made to not only assess 75-100 cells per endothelial image, but that this number ...Continue Reading

References

Jul 1, 1979·Ophthalmology·G N RaoJ V Aquavella
Jul 1, 1992·Experimental Eye Research·M J Doughty
Aug 1, 1980·Archives of Ophthalmology·G N RaoJ V Aquavella
Sep 1, 1993·Optometry and Vision Science : Official Publication of the American Academy of Optometry·M J DoughtyK Trang Nguyen
Apr 28, 2006·Investigative Ophthalmology & Visual Science·Henry F Edelhauser
Oct 18, 2011·International Ophthalmology·Meltem YagmurKemal Yar
Jul 15, 2015·Graefe's Archive for Clinical and Experimental Ophthalmology = Albrecht Von Graefes Archiv Für Klinische Und Experimentelle Ophthalmologie·Dong-Hyun KimJoon Young Hyon

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Citations

Sep 13, 2021·Optometry and Vision Science : Official Publication of the American Academy of Optometry·Zalak ShahShwetambari Singh

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