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B. Golebiowski, E. Papas, F. Stapleton; Clinical Comparison of the CRCERT-Belmonte and Cochet-Bonnet Aesthesiometers. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2376.
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© ARVO (1962-2015); The Authors (2016-present)
The Cochet-Bonnet (CoBo) is the most widely used aesthesiometer in studies which examine ocular surface sensitivity. However, it has critical limitations resulting in development of newer instruments, such as the CRCERT-Belmonte aesthesiometer (CBA). This study compares corneal sensitivity results obtained with the CBA and the CoBo, in order to examine the relationship between measurements made with the two instruments.
Corneal sensation threshold was measured in 18 subjects with normal corneas (8M:10F, 34.4±8.0yrs) using the CBA and the CoBo aesthesiometers. Measurements were carried out on the corneal apex of the right eye only. The order in which the instruments were used was randomised. The CoBo was used with both the 0.08 and 0.12mm diameter filaments (CoBo 0.08 and CoBo 0.12). Threshold to stimulation was determined using the ascending method of limits. Pearson’s correlation and Spearman’s rho were used to examine the relationship between threshold results with the CBA and the CoBo. All results were converted to force and pressure and the degree of agreement between measurements made with the CBA and the CoBo was determined using the statistical approach of Bland & Altman and the Wilcoxon Signed rank test. A 95% confidence level was considered statistically significant.
Mean group corneal thresholds to stimulation were: 64.4±29.4 ml/min with the CBA; 4.5±1.2 cm with the CoBo 0.08; 5.5±0.8 cm with CoBo 0.12. Threshold results for 10 of 18 subjects were outside the stimulus range of the CoBo 0.12 and 2 were outside the range of either CoBo filament. All measurements were within the stimulus range of the CBA. No correlation was found between threshold measured with the CBA and that measured using the CoBo 0.08 or 0.12. In terms of force exerted by the stimulus, corneal threshold was measured to be higher with the CoBo than with the CBA by 0.01mN (CoBo 0.08) and 0.05mN (CoBo 0.12) (p<0.02). Likewise with respect to pressure, threshold was measured to be higher with the CoBo than with the CBA.
Corneal sensitivity measurements made with the CBA and the CoBo are not comparable, probably due to dissimilarities in the composition of their stimuli and thus mode of stimulation. The underestimation of corneal sensitivity by the Cochet-Bonnet aesthesiometer and its inability to measure sensitivity on a proportion of subjects are important considerations in the measurement of sensitivity loss, as this instrument is unlikely to detect subtle changes, particularly at higher sensitivity levels.
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