Which instrument is used to measure the curvature of the cornea?

The keratometer is the instrument specifically designed to measure the curvature of the cornea. This measurement is crucial for various purposes, including fitting contact lenses, diagnosing and monitoring keratoconus, and planning for refractive surgery. The keratometer uses reflected light to determine the curvature by measuring the radius of curvature of the corneal surface.

In contrast, a lensmeter is used to measure the power of lenses, not the curvature of the cornea. A topographer can provide detailed mapping of the cornea's surface and is effective for assessing irregularities, but its primary function extends beyond just measuring curvature to provide a more comprehensive view of the corneal shape. A phoropter is primarily used in eye examinations to determine a patient's refractive error and prescribe corrective lenses, rather than measuring the cornea itself. Therefore, the correct choice is the keratometer for its specific role in assessing corneal curvature.