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The assessment of automated measures of hydrogel contact lens refractive index
Author(s) -
Nichols Jason J.,
Berntsen David A.
Publication year - 2003
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.2003.00147.x
Subject(s) - refractometer , intraclass correlation , refractive index , contact lens , operator (biology) , reliability (semiconductor) , lens (geology) , mathematics , optics , index (typography) , materials science , computer science , statistics , chemistry , reproducibility , physics , biochemistry , power (physics) , repressor , quantum mechanics , world wide web , transcription factor , gene
Abstract Purpose: To investigate within‐ and between‐operator reliability and validity of refractive index measures of hydrogel lenses. Methods: Twenty‐three lenses of various nominal water contents were examined by two operators on two occasions separated by 1 h. An automated refractometer (CLR 12‐70, Index Instruments, Cambridge, UK) was used for refractive index measures. Lenses were presented in a random order to each operator by a third party, and operators were masked to any potential lens identifiers. Intraclass correlation coefficients (ICC), 95% limits of agreement (LoA), and paired t ‐tests were used to characterize the within‐ and between‐operator reliability and validity of lens refractive index measures. Results: The mean (±S.D.) difference between sessions was 0.0001 ± 0.0011, which did not significantly differ from zero ( p = 0.64). Within‐operator reliability was excellent (ICC = 0.9990, 95% LoA = −0.0021 to 0.0024). The mean (±S.D.) difference between‐operators was 0.0002 ± 0.0010, which was not significantly different from zero ( p = 0.54). Between‐operator reliability was also excellent (ICC = 0.9984, 95% LoA = −0.0026 to 0.0029). The mean difference between the nominally reported refractive index and our refractive index measures was −0.0009 ± 0.082, which did not differ statistically from zero ( p = 0.52); the 95% LoA for this difference was −0.0152 to 0.0169. Conclusion: There is good reliability within‐ and between‐operators in measuring the refractive index of hydrogel lenses using the CLR 12‐70 automated refractometer.