Which condition is characterized by a gray band of opacity in the cornea encircling the iris?

The condition characterized by a gray band of opacity in the cornea surrounding the iris is known as arcus senilis. This occurs as a result of lipid deposits in the cornea, which manifest as a gray or white arc that may become more prominent with age. Arcus senilis typically does not cause any symptoms and is often considered a normal part of aging, particularly in older adults.

In contrast, corneal abrasions are superficial scratches on the cornea that lead to pain, redness, and tearing without producing the characteristic gray band. Corneal ulcers are open sores on the cornea, often associated with infections or trauma, and can lead to significant vision loss if untreated; they also do not present with the specific gray opacity seen in arcus senilis. Herpetic infections of the eye involve viral keratitis, resulting in symptoms like pain, redness, and vision changes, but again do not produce the distinct gray ring. Thus, among the conditions listed, arcus senilis is the one that specifically presents with the gray band of opacity encircling the iris.