Which type of animal has very strong palpebral muscles, making assistance necessary for applying ophthalmic drugs?

Equines, or horses, have particularly strong palpebral muscles, which are the muscles controlling the eyelids. These muscles allow horses to close their eyes tightly. This characteristic makes it difficult to easily administer ophthalmic medications without assistance. When applying drops or ointments to the eyes of horses, handlers often need to restrain the animal or employ specific techniques to keep the eyes open and ensure proper application, as the strong palpebral response can cause the animal to resist.

In contrast, while felines and canines also have palpebral muscles that may require some level of restraint for drug administration, they are generally not as strong or effective at preventing medication application as in equines. Rodents can typically be restrained easily, allowing for straightforward administration of topical medications without the need for significant assistance. Understanding the anatomical and behavioral differences in these species is crucial for effective veterinary practice.