Comparison of Cochet-Bonnet, Dental Floss, and Cotton Wisp With Applications to Corneal Sensation Testing

The measurement of corneal sensation can be useful in the diagnosis of corneal neuropathies. Although the Cochet-Bonnet (CB) esthesiometer is the gold standard, cotton wisp (CW) and dental floss are commonly used in clinical practice.

We assessed the steady-state force of thick dental floss (tkDF), thin dental floss (tnDF), and CW compared with that of CB. We surveyed cornea/refractive specialists (CRS) and noncornea/refractive specialists (NCRS) for frequency and method by which corneal sensation was checked.

Compared with CB, the maximum force applied by tkDF was 0.92 grams more ( P < 0.05), 0.15 grams more for tnDF ( P < 0.05), and 0.23 grams less for CW ( P < 0.05). Compared with CB, force per unit length was 0.13 g/mm higher for tkDF ( P < 0.05), 0.001 g/mm higher for tnDF ( P = 0.44), and 0.008 g/mm lower for CW ( P = 0.10). We collected responses from 182/284 CRS and 102/284 NCRS. 12/182 CRS checked cornea sensation 0x/month compared with 42/102 NCRS. A total of 103/182 CRS and 54/102 NCRS checked cornea sensation 1-5x/month. CW was the most common tool used for CRS (115/170) and NCRS (53/60).

tnDF provides the best analog for the CB. CW provides a small amount of force over a large range of lengths and may be a useful screening tool. tkDF is less suitable for screening. CRS check corneal sensation at a higher rate than NCRS. CW was the most common method used in both groups.