Which anatomical feature distinguishes the angle at either end of the eyelid slit?

The anatomical feature that distinguishes the angle at either end of the eyelid slit is known as the canthus. In the anatomy of the eye, the canthus refers to the corners where the upper and lower eyelids meet. There are two canthi: the medial canthus, which is located closer to the nose, and the lateral canthus, situated toward the outer side of the eye. The canthi play a role in the drainage of tears, as they are associated with the lacrimal system.

The other options, while related to the eye, represent different structures. The cornea is the clear, front surface of the eye that helps focus light; the limbus is the border between the cornea and the sclera; and the retina is the light-sensitive layer at the back of the eye that converts light into neural signals. Understanding each of these anatomical features allows for a better grasp of eye function and structure as a whole.