Which optical instrument is primarily used for measuring the curvature of the cornea?

The keratometer is an optical instrument designed specifically for measuring the curvature of the cornea. This device plays an essential role in refractive surgery assessments, contact lens fitting, and understanding the overall shape of the cornea, which can affect vision. The keratometer utilizes reflected light to measure the radius of curvature of the corneal surface, thereby providing important data regarding the eye's refractive characteristics.

Other instruments serve different purposes in ophthalmology. For instance, an ophthalmoscope is used for inspecting the retina and other internal structures of the eye but does not measure corneal curvature. A lensmeter, on the other hand, measures the power of lenses, which is important for determining prescriptions but does not relate to the measurements of the cornea. Lastly, a pachymeter measures corneal thickness, a different parameter crucial in assessing conditions like glaucoma but not related to curvature.