Which clinical sign is associated with Keratoconjunctivitis sicca?

Keratoconjunctivitis sicca, also known as dry eye, is a condition characterized by insufficient tear production which can lead to inflammation and various ocular signs. The presence of mucopurulent discharge is indeed a notable clinical sign associated with this condition. The lack of adequate tears causes the ocular surface to become dry and irritated, leading to secondary infections and inflammation. As a result, the eyes may produce mucus and pus, contributing to the mucopurulent discharge observed in affected animals.

In contrast, a normal corneal reflection indicates a healthy ocular surface, while pupil constriction is typically related to other conditions involving the iris or abnormal responses to light rather than dry eye. Decreased intraocular pressure does not directly link to Keratoconjunctivitis sicca, as this condition primarily affects tear production and not the pressures within the eye. Thus, the mucopurulent discharge stands out as a key clinical sign indicative of Keratoconjunctivitis sicca, confirming the correctness of the answer.