In what unit is keratometry expressed?

Keratometry is a measurement related to the curvature of the cornea, which is crucial in evaluating the eye's shape and how it refracts light. It specifically quantifies the anterior surface of the cornea in terms of its power to bend light. The unit "diopters" is used to express this power, which relates to the focal length of the curvature being measured.

In the context of keratometry, the diopter measurement indicates how strongly the cornea converges or diverges light; a higher diopter value corresponds to a steeper curvature. Therefore, diopters are the standard unit used in ophthalmology to express the refractive power of lenses or the curvature of the cornea, making this choice the correct one for this question.