Which of the following is characterized by a gray ring on the cornea, especially in older adults?

The correct answer, Arcus senilis, is a condition characterized by a gray or white arc that appears along the outer edge of the cornea, typically seen in older adults. This condition is caused by the deposition of lipids in the corneal stroma, which is a common age-related change. Arcus senilis is generally benign and does not affect vision. Its presence can sometimes indicate elevated cholesterol levels, but in older individuals, it is often simply a physiological change.

Understanding why arcus senilis appears in older adults is important; as people age, lipid metabolism changes, leading to these deposits without any other significant health implications. Unlike conditions that may indicate underlying disease, arcus senilis is primarily associated with aging.

In contrast to this condition, pinguecula appears as a yellowish, raised growth on the conjunctiva and is related to environmental factors, such as UV light exposure. A corneal ulcer is a defect in the corneal epithelium that can occur due to infection or trauma. Keratoconus, on the other hand, is a progressive thinning of the cornea that results in a cone-shaped bulge, affecting vision.