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2
INTRODUCTION
2.1
Outline
2.1.1
Device outline
The NIDEK HANDHELD REF/KERATOMETER, HandyRef-K, measures spherical, cylindrical refrac-
tive errors, and cylinder axis from the refractive status of the patient’s eye.
The keratometer measures the corneal curvature radius (corneal refractive power) in the steepest and
flattest meridian directions, cylinder axis, and corneal cylindrical power.
This device is a hand-held model that allows measurement of children who cannot hold their head on
the stationary chinrest, bed-ridden patients or patients in an operating room.
2.1.2
Intended use
The HANDHELD REF/KERATOMETER, HandyRef-K, is a medical device which measures objective
refractive errors and corneal curvature radius of the patient’s eye.
2.1.3
Principles
Objective refractive error measurement
Fine measurement beams are projected on the fundus of the patient’s eye by a projecting optical
system and then the ring image obtained from the reflected beams is used for computation to
determine the refractive errors (SPH, CYL, AXIS) of the patient’s eye.
Corneal curvature radius measurement
The image of the mire ring projected on the patient’s cornea is captured and used for computa-
tion to determine the corneal curvature radius (refractive power) in the steepest and flattest
meridian directions, cylinder axis, and corneal cylindrical power.
