What instrument is used to measure the curvature of the central part of the cornea?

The keratometer is the correct instrument used to measure the curvature of the central part of the cornea. This device is crucial in ophthalmology, particularly for assessing the shape of the cornea, which is significant for various procedures, including fitting contact lenses and planning refractive surgeries like LASIK.

The keratometer works by projecting a series of light rings onto the cornea and measuring the reflection of these rings. The curvature data it provides helps in diagnosing conditions such as astigmatism and informs the selection of the appropriate contact lens shape.

In contrast, other instruments have different functions. An ophthalmoscope is designed for examining the interior of the eye, focusing on the retina and optic nerve but not measuring corneal curvature. The tonometer is used to measure intraocular pressure and assess for glaucoma, while the keratoscope can assess the overall topography of the cornea but not specifically measure its curvature in a precise manner like the keratometer does. Thus, the keratometer is specialized for the task of measuring corneal curvature accurately.