Which condition is characterized by a cone-shaped protrusion of the cornea?

Keratoconus is a condition where the normally dome-shaped cornea gradually becomes thinner and develops a cone-like bulge. This protrusion can lead to significant changes in vision due to the irregular shape, which disrupts the light entering the eye and can cause blurry vision, distortion, and increased sensitivity to glare. The unique corneal shape associated with keratoconus typically manifests in young adulthood and can progress over time, making early detection and management crucial.

In contrast, ametropia refers to any refractive error in which the eye does not focus light evenly onto the retina, resulting in nearsightedness, farsightedness, or astigmatism, but it does not involve changes to the cornea's shape. Asthenopia, commonly known as eye strain, is a temporary condition resulting from prolonged use of the eyes, particularly when reading or using computers, and does not involve structural changes to the cornea. Diplopia, or double vision, can arise from various issues but is not specifically related to the morphology of the cornea and does not describe a protrusion.