PURPOSE: Arbitrary numbers of corneal confocal microscopy images have been used for analysis of corneal subbasal nerve parameters under the implicit assumption that these are a representative sample of the central corneal nerve plexus. The purpose of this study is to present a technique for quantifying the number of random central corneal images required to achieve an acceptable level of accuracy in the measurement of corneal nerve fiber length and branch density. METHODS: Every possible combination of 2 to 16 images (where 16 was deemed the true mean) of the central corneal subbasal nerve plexus, not overlapping by more than 20%, were assessed for nerve fiber length and branch density in 20 subjects with type 2 diabetes and varying degrees of functional nerve deficit. Mean ratios were calculated to allow comparisons between and within subjects. RESULTS: In assessing nerve branch density, eight randomly chosen images not overlapping by more than 20% produced an average that was within 30% of the true mean 95% of the time. A similar sampling strategy of five images was 13% within the true mean 80% of the time for corneal nerve fiber length. CONCLUSIONS: The "sample combination analysis" presented here can be used to determine the sample size required for a desired level of accuracy of quantification of corneal subbasal nerve parameters. This technique may have applications in other biological sampling studies.
PURPOSE: Arbitrary numbers of corneal confocal microscopy images have been used for analysis of corneal subbasal nerve parameters under the implicit assumption that these are a representative sample of the central corneal nerve plexus. The purpose of this study is to present a technique for quantifying the number of random central corneal images required to achieve an acceptable level of accuracy in the measurement of corneal nerve fiber length and branch density. METHODS: Every possible combination of 2 to 16 images (where 16 was deemed the true mean) of the central corneal subbasal nerve plexus, not overlapping by more than 20%, were assessed for nerve fiber length and branch density in 20 subjects with type 2 diabetes and varying degrees of functional nerve deficit. Mean ratios were calculated to allow comparisons between and within subjects. RESULTS: In assessing nerve branch density, eight randomly chosen images not overlapping by more than 20% produced an average that was within 30% of the true mean 95% of the time. A similar sampling strategy of five images was 13% within the true mean 80% of the time for corneal nerve fiber length. CONCLUSIONS: The "sample combination analysis" presented here can be used to determine the sample size required for a desired level of accuracy of quantification of corneal subbasal nerve parameters. This technique may have applications in other biological sampling studies.
Authors: Mitra Tavakoli; Maryam Ferdousi; Ioannis N Petropoulos; Julie Morris; Nicola Pritchard; Andrey Zhivov; Dan Ziegler; Danièle Pacaud; Kenneth Romanchuk; Bruce A Perkins; Leif E Lovblom; Vera Bril; J Robinson Singleton; Gordon Smith; Andrew J M Boulton; Nathan Efron; Rayaz A Malik Journal: Diabetes Care Date: 2015-01-29 Impact factor: 19.112
Authors: B Köhler; S Allgeier; A Bartschat; R F Guthoff; S Bohn; K-M Reichert; O Stachs; K Winter; R Mikut Journal: Ophthalmologe Date: 2017-07 Impact factor: 1.059
Authors: Anders H Vestergaard; Keea T Grønbech; Jakob Grauslund; Anders R Ivarsen; Jesper Ø Hjortdal Journal: Graefes Arch Clin Exp Ophthalmol Date: 2013-06-22 Impact factor: 3.117
Authors: Ahmad Kheirkhah; Rodrigo Muller; Janine Mikolajczak; Ai Ren; Ella Maria Kadas; Hanna Zimmermann; Harald Pruess; Friedemann Paul; Alexander U Brandt; Pedram Hamrah Journal: Invest Ophthalmol Vis Sci Date: 2015-09 Impact factor: 4.799