Nidek Medical ARK-1S, Руководство оператора

Страница: 15 / 112

9
2
INTRODUCTION
2.1 Device Outline

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 per-
formed 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.
2.1.1 Intended use
The AUTO REF/KERATOMETER ARK-1s is a medical device which measures objective, subjective
refractive errors, and corneal curvature radius of the patient’s eye. This device also offers retroillumi-
nation mode for observing the condition of the ocular media, and measures the amplitude of accom-
modation.
2.1.2 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.
Subjective refractive error measurement
The chart for which the refraction distance is optically corrected and trial lens located in the line
of the patient’s eye allow the subjective refractive error measurement and visual acuity test. The
spherical power of trial lenses is changed by adjusting the distance from 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) and the principal meridian direc-
tions.
Retroillumination mode
Light is shone into the eye and an image obtained by the reflected light from the fundus allows
the condition of the ocular media to be observed.
Accommodation measurement
Continuous refractive error measurement based on the objective refractive errors taken of the
patient’s eye while fixated on a moving a chart allows accommodation to be determined.