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

The keratometer is specifically designed to measure the curvature of the cornea, which is crucial for assessing the eye's refractive properties and diagnosing various eye conditions. This tool works by projecting a series of illuminated rings onto the cornea and measuring the reflection of these rings, allowing the optometrist or ophthalmologist to determine the corneal curvature accurately.

In contrast, a refractometer is used primarily to measure the refractive indices of lenses and the eye, which helps in determining the prescription for glasses or contact lenses rather than the curvature of the cornea itself. An ophthalmoscope is an instrument used to examine the interior structures of the eye, such as the retina and the optic nerve, but it does not measure curvature. The phoropter is a device used during vision examinations to determine an individual's prescription for corrective lenses; while it helps in assessing visual acuity and refractive error, it does not directly measure corneal curvature. Thus, the keratometer is the appropriate tool for this specific measurement.