APC AR1100 Betreibershandbuch PDF herunterladen (Seite 17)

BEFORE USE: Principles

1.3 Principles

1. Objective refraction

Fine measurement beams are projected on the fundus of the patient’s eye by a projecting

optical system and then computation is performed by capturing the reflected beams as a

ring image to measure the refractive errors (SPH, CYL, AXIS) of the patient’s eye.

2. Corneal curvature radius measurement

Four near-infrared rays area projected onto the cornea and the ray reflected by the cornea is

detected. From the detected signals, the corneal curvature radius (refractive power) and the

direction of the steepest meridian are measured.

3. Measurement of intraocular pressure (NT measurement)

Based on the Imbert-Fick principle (W = Pt × A), the intraocular pressure is calculated by

dividing the amount of air pressure into the area of applanated surface.

The device increases the air pressure puffed onto the cornea in proportion to time. The

shape of the cornea changes gradually in the order of convex surface

→ applanated surface

→ concave surface. This change is optically detected and the device calculates the time

required to make the pressed area flat after air is puffed on it. The air pressure used to make

the cornea flat is calculated by time, and finally the intraocular pressure is obtained.

APC (Automatic Puff Control) function

The intraocular pressure measurement is performed with the air pressure as low as possible. When

the measurement range is set to “APC 40” or “APC 60”, in the first measurement, the automatic

shut-off function, which stops puffing air as soon as the light reflected from the cornea is detected,

activates in order to eliminate excessive puffing.

In subsequent measurements, the APC function activates to perform the measurement with the

minimum air pressure based on the former measurement data.

As the patient's eye is protected from excessive air pressure, discomfort of the patient can be

decreased and continuous measurement can be performed smoothly.

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APC AR1100 Betreibershandbuch Seite 17