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000000Ć1150Ć839 IOLMaster 11.02.2004
Start the measurement using the pushbutton on the joystick.
Note:
Before taking the measurement, tell the patient once more to
fixate the red fixation light, which lights more intensively during
the measurement. If the patient's visual acuity is poor, ask if she
or he can see the fixation point! If not, erroneous measurements
cannot be precluded.
In the case of poor visual acuity/high ametropia (>
±
6 D), it is
advisable to measure through the glasses. If taken conscienĆ
tiously, such measurements will not produce erroneous results.
Measurements through contact lenses will lead to measuĆ
rement errors and therefore should not be performed
.
In the status bar, a blue progress bar appears. The corresponding display
field beside the video image shows the measured axial length. The video
image is overlaid with a graph similar to those known from ultrasonic
measuring instruments. At the same time, the axial length and the
signalĆtoĆnoise ratio (SNR) of the measuring signal are being displayed.
The SNR is a measure of the quality of measurement. Measurements
with an SNR between 1.6 and 1.9 appear with an exclamation mark
after the measured value. At the same time, the message "Borderline
SNR" appears on the display (Refer to the section
PostĆrun editing of
axial length measurements
,
p. 56 ff
.
,
for the assessment of the SNR).
With stronger lens opacities, it may be advisable to defocus the instruĆ
ment. You may choose a reflection (
2
, Fig. 16) as large as the circle on
the display. If even then measurements are impossible, refocus the
instrument and shift the reflection to the bottom and/or top margin of
the circle on the display by varying the vertical adjustment (turning
joystick).
Note:
Defocusing and shifting the reflection within the circle is
without any effect on the result, because interferometric
axial length measurement is absolutely distanceĆindeĆ
pendent.
If a valid measurement is achieved, you may assume that the
displayed result is the correct axial length.
By pressing the pushbutton on the joystick the next measurement of
this eye is being started. It is possible to take up to 20 of such
measurements per eye on one day.
Caution:
Avoid measurements of eyes with retinal detachment. In this case,
erroneous measurements cannot be precluded.
Operation
