Page 6 of 87 DGH 55B-INS-OMENG Rev: 3
1. Introduction
1.1 General Device Description
The DGH 55B Ultrasonic Pachymeter (Pachmate 2) is a handheld, battery operated, ultrasonic
device that is used in the ophthalmic field for measuring the thickness of the human cornea.
Cornea thickness measurements are used in the preoperative evaluation of laser vision correction
procedures, and for the evaluation of glaucoma. The DGH 55B is also used as a diagnostic tool
in a variety of clinical situations including the general assessment of corneal health related to
pathologies and in evaluating corneal swelling following surgery or injury.
The general principle of operation of the DGH 55B Ultrasonic Pachymeter (Pachmate 2) is as
follows: The tip of the ultrasonic transducer (probe) is placed in contact with the patient’s cornea
which automatically initiates a measurement cycle. At the start of the measurement cycle, the
electronic circuit board transmits voltage pulses to the ultrasonic transducer (probe). The
piezoelectric element in the transducer converts these voltage pulses into ultrasonic energy,
sending a pulse of a high frequency sound waves (20MHz damped to 13MHz) through the eye,
and reflected pulses (echos) are received back to the transducer and are converted to voltage
pulses. The first echo to be received comes from the anterior corneal surface. If an echo spike
from the anterior corneal surface is received within an anticipated time window, the DGH 55B
then prepares to receive an echo spike from the posterior corneal surface. Only anterior and
posterior echo spikes that fall within specified voltage limits that ensure that the probe tip is
perpendicular to the cornea surface are accepted for processing. The time interval between the
accepted anterior and posterior echo spikes represents the thickness of the cornea. The time
interval is converted to a corresponding distance, or thickness, based on the acoustic velocity
through the cornea, and is displayed on the 16 x 2 LCD in units of microns.
1.2 Device Classification
Device: System, Imaging, Pulsed Echo, Ultrasonic Device: Diagnostic Ultrasonic Transducer
Panel: Radiology Panel: Radiology
Product Code: IYO Product Code: ITX
Device Class: II Device Class: II
Regulation Number: 21 CFR 892.1560 Regulation Number: 21 CFR 892.1570
1.3 Indications For Use
The DGH 55B Ultrasonic Pachymeter (Pachmate 2) is a handheld, battery operated, ultrasonic
device that is used in the ophthalmic field for measuring the thickness of the human cornea.
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