The NIDEK AUTO REF/KERATOMETER ARK-1s measures spherical, cylindrical refractive errors, and cylinder axis from the refractive status of the patient’s eye. In addition, subjective test is performed with the built-in charts and lenses for subjective measurement. The keratometer measures the corneal curvature radius (corneal refractive power), principal meridian directions, and corneal cylindrical power.
A bench-top, mains electricity (AC-powered) ophthalmic instrument designed to measure the curvature of the anterior surface of the cornea, particularly for determining the presence, extent, and axis of astigmatism (an error of refraction in the eye due to the cornea being unequally curved in different directions, so that rays of light in different meridians cannot be brought to focus together on the retina). It actually measures the radius of curvature in millimetres but typically displays it in dioptres. It is used mainly for contact lens fitting and for intraocular lens power determination prior to cataract surgery. This device is also known as an ophthalmometer.
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