Corneal touch threshold (CTT) was measured in the right eye of each horse in the nasal, ventral, dorsal and temporal regions, approximately 2mm from the limbus, and in the center of the cornea, using a Cochet-Bonnet esthesiometer
(Luneau Ophthalmologie, Chartres Cedex, France) (Figure 1).
As such, the following signs and symptoms were clinically and qualitatively assessed: loss of sensitivity (evaluated with an esthesiometer
), lymphadenopathy, arthralgia, nerve pain, edema, weight loss, neural thickening, fever, malaise, myalgia, orchitis, paresthesia, hyperesthesia, and nasal and visual complaints.
Historically, touch sensitivity of the ocular surface has been measured using a von Frey and later Cochet-Bonnet esthesiometer
(Figure 2) , where a mechanical stimulus is delivered using hair or nylon filaments of variable diameter and length.
(64) evaluated 94 cases to determine whether DSEPs, biothesiometer, or the Semmes-Weinstein esthesiometer
had higher sensitivity for detecting lumbar radiculopathies.
Stanley Hall dripped spirit of camphor into her mouth, causing blisters to form on her lips and tongue, and bruised her arm with an esthesiometer
that tested for the sensation of pressure and resulted in the loss of the use of her hand for several days.
Touch threshold can be quantified by the Semmes-Weinstein monofilament pressure esthesiometer
, (25) although an engineering analysis (26) of this device revealed that it has several limitations.