What is the corneal lesion characterized by a black or brown spot in a cat known as?

Corneal sequestration is a condition specifically observed in cats where a distinct area of the cornea develops a black or brown pigmentation, often due to an underlying disease such as chronic irritation, corneal damage, or other etiological factors. This pigmentation arises as a result of necrosis and the accumulation of melanin in the affected area. It is a unique finding characteristic of feline eyes and is often associated with conditions like feline herpesvirus infection, which may lead to chronic corneal changes.

In contrast, keratitis refers to inflammation of the cornea that does not specifically present as a black or brown spot. Corneal ulcers involve the erosion of the corneal surface, usually manifesting as discoloration or opacity, but not typically as a black or brown lesion. Corneal degeneration involves changes in the cornea's structure, often leading to cloudiness or other alterations, and does not specifically describe a pigmented lesion. Thus, the distinct appearance and underlying pathology of corneal sequestration make it the correct answer for the condition described in the question.