Measurement of corneal sensitivity in 20 ophthalmologically normal alpacas

Abstract

Objective: To determine corneal sensitivity in 20 healthy adult alpacas (40 eyes) in order to establish reference values.

Design: Prospective study.

Animals: Twenty healthy, adult alpacas.

Procedures: Corneal sensitivity was determined by the corneal touch threshold (CTT) using a Cochet-Bonnet esthesiometer. Five different regions of the cornea were evaluated (nasal, ventral, lateral, dorsal, and central).

Results: Corneal touch threshold values (in mm filament length) obtained from five corneal regions demonstrated varying corneal sensitivities. The central region (34.5 ± 7.1 mm) was the most sensitive, followed by the ventral (29.5 ± 7.2 mm), medial (29.3 ± 7.3 mm), dorsal (25.6 ± 6.3 mm), and lateral (21.8 ± 5.7 mm) regions. All pairwise comparisons of regional differences were statistically significant (P < 0.05), except for the comparison between the ventral and medial regions (P = 0.88). Evaluation of the CCT while controlling for age (2-5 years vs. 6-10 years) demonstrated an increased CTT with an increasing age for the central, ventral, medial and lateral regions. A decrease in the CTT of the dorsal region was noted with increasing age.

Conclusion and clinical relevance: Corneal touch threshold values in 40 eyes of 20 healthy adult alpacas were determined using a Cochet-Bonnet esthesiometer. This study demonstrated the central corneal region to be most sensitive. Values obtained may serve as reference values in subsequent studies.