What condition is characterized by severe chemosis in cats?

Severe chemosis, which is the swelling of the conjunctiva, is notably associated with chlamydial conjunctivitis in cats. This condition is caused by the bacterium Chlamydia felis, which leads to significant inflammation and edema of the conjunctival tissues.

In chlamydial conjunctivitis, one of the hallmark symptoms is the presence of severe chemosis, often accompanied by conjunctival hyperemia and discharge. The condition is particularly prevalent among younger cats and can cause significant discomfort and irritation.

While other conditions listed, such as feline herpesvirus infection, allergic conjunctivitis, and corneal ulceration, can also cause eye-related symptoms, they typically do not present with the same degree of conjunctival swelling or chemosis as seen with chlamydial conjunctivitis. Feline herpesvirus infection and allergic conjunctivitis tend to produce more variable clinical signs, while corneal ulceration primarily affects the cornea rather than causing severe conjunctival swelling. Therefore, when identifying the condition characterized by severe chemosis, chlamydial conjunctivitis is the most fitting diagnosis.