Tomey UD-600, Operator'S Manual

Page: 132 / 262

3-104
e) What is a good waveform
<Contact mode>
In the auto measurement, the waveforms which satisfy
the following conditions
A to C are considered to be
preferable waveforms as measurement data.
A
The following waveforms stand high from the level
cursor line position.
„ Normal
Lens front waveform/retinal waveform
„ Dense Cataract
Lens front waveform/retinal waveform
„ Aphakic
Retinal waveform
„ Pseudophakic
Lens front waveform/retinal waveform
B The retinal waveform stands in vertical (Ultrasound
wave vertically contacts with the retina.)
If the wave inclines, a longer measurement tends to
be resulted.
C
Less fluctuations with measurement data
The following items are used to check if the ultrasound
waves properly catch the optical axis correctly and if the
ideal waveforms are obtained.
i) The highly rising retinal waveform indicates that re-
lated ultrasound waves have vertical contact with the
retina.
ii) The highly rising lens front/rear waveforms indicate
that the ultrasound waves correctly catch the optical
axis.
iii) The distinctive retinal and sclerotic waves imply that
the ultrasound waves have vertical contact with the
retina.
This distinction of these two waves is not always re-
quired for the case set with high gain, since the drop
(chorioid) between the two waveforms cannot be
checked.
iv) The initial waveform (corneal waveform), if having
no tail behind the waves, implies that the biometry
probe has direct contact with the cornea.
If tears or corneal protective media exists between the
probe and the cornea, the corneal wave has a tail at
the end. If this occurs, related measurement data will
be unstable or resulted in longer measurement length.
Fall between retina and sclera (choroids)
Level Cursor/Line
RETINA
SCLERA
Sharp rise
RETINA SELECTING
CURSOR
ACD LENS AXIAL
3.6 Biometry