Cochet-Bonnet aesthesiometer-determined corneal sensitivity in neonatal foals and adult horses.

This study evaluates corneal sensitivity and tear production in healthy adult horses, healthy foals, and sick foals using a Cochet-Bonnet aesthesiometer. The research reveals that adult horses possess greater corneal sensitivity than both healthy and ill foals, with illness exacerbating this gap. Shrinkage in tear production was also observed among foals, compared with adults, possibly contributing to slow corneal healing and ulcerative keratitis.

Measuring Corneal Touch Threshold

• The key measure used in this study is the Corneal Touch Threshold (CTT), determined using a Cochet-Bonnet aesthesiometer.
• This tool measures the sensitivity of the cornea, the outermost layer of the eye, to touch.
• The means CTT for adult horses, healthy foals, and sick foals were compared, revealing differences in corneal sensitivity across these groups.

Corneal Sensitivity in Horses and Foals

• Adult horses displayed a higher mean CTT, signaling greater corneal sensitivity, as compared to both healthy and ill foals.
• Interestingly, the central portion of the cornea in adult horses was found to be more sensitive than the limbal cornea, the border region between the cornea and the sclera, the white part of the eye.
• Sick neonatal foals showed a significant reduction in corneal sensitivity compared to the adults. This alludes to illness further diminishing the already lower corneal sensitivity in foals.

Tear Production

• Another important aspect examined is the Schirmer I tear test values, designed to measure tear production.
• The result recorded lower values in foals, both healthy and sick, compared to adult horses. This indicates a reduced tear production rate among these younger animals.

Link to Medical Conditions

• The reduced corneal sensitivity and lower tear production observed in foals could have potential health implications.
• The researchers suggest a link between these factors and slower corneal healing and a higher risk of ulcerative keratitis—a painful condition involving inflammation and ulceration of the cornea.