Nidek ARK-500A Auto Refractor/Keratometer

The NIDEK ARK-500A is an autorefractor/keratometer which contains both
a refractormeter and keratometer in one unit.
The refractometer objectively measures refractive errors of sphere, cylinder,
and axis for lenses that correct the patient’s vision into emmetropia.
The ketatometer measures the corneal curvature radius (corneal refractive power),
principal meridian direction and corneal cylendrical power.
Refraction is mainly performed as a reference for lens prescrition
to correct the visual acuity using glasses or contact lenses.