IOLMaster — Keratometer Measurements.
Now and then, there are reports on different K readings on the IOL Master
as compared to other keratometers. Also, discrepancies in IOL powers
are reported comparing IOL Master results with those obtained on ultrasound
equipment, even when the same input data was used.
Very often, the described problems can be traced down to keratometer
indices and/or to peculiarities of corneal power implementations in the
IOL formulas of the respective instruments.
Measurement of Corneal Curvature (KER)
1. Activate Keratometer Measurement Mode:
- clicking on the KER icon
- pressing the
- pressing the <SPACE BAR> in ALM mode (ALM)
2. Tell the patient to focus on the yellow light .
3. Align the IOLMaster.
The 6 peripheral
measuring points should be symmetrical to the circular cross-hair and appear
optimally focused. The central point is usually not
focused and is not evaluated
for keratometer measurement.
Ensure that all 6 peripheral points are visible and located in the
field between the two auxiliary circles on the display. It is
recommended that the patient blink his/her eye shortly before
the measurement to produce a continuous tear film. This will
improve the reflectivity of the cornea. The measuring points
should be circular or ellipsoid. If the measuring points are
irregular (i.e. corneal scar), measurement is not possible. Precise
measurements are possible only if the 6 peripheral measuring
points appear optimally focused on the display. In the case of dry
eyes, a tear fluid substitute may help to obtain a reliable
4. Take the measurement by pressing the button on the joystick.
Five internal measurements will be taken within the space of 0.5 s. The
end of the measurements is indicated by a short acoustic signal.
Following this, the radii or corneal K's (depending on program settings)
of the two main sections will be displayed, together with the respective
axial orientation and the astigmatic difference. In the case of a spherical
cornea, only the radius or a corneal K will be displayed, but no axial
orientation or astigmatic difference. A blue progress
bar in the status
bar will indicate the progress of computation.
The size and shape of measurement points are verified by the software.
If a measurement point is not correctly identified, a blue flashing dot
In the printout this will be marked by an x. These readings
should not be used and a new measurement should be taken as a
Keratometer measurements may be repeated as often as desired;
however, only the last three measurements will be displayed.
The IOLMaster requires three measurements to be taken! The
message Measure again will thus appear. Only then will a mean
value be passed on to the IOL calculation and an evaluation
enabled. Only the number of measurements is crucial here.
To restore the last (just overwritten) readings, press shortcut keys
+ <Z> (UNDO function is irrevocable).
To delete one of the three displayed readings, select it and press the
<DEL> key. Now confirm with YES.
If the last three readings differ by > 0.5 dpt (mean value of the spherical
equivalent of the last three measurements) or if the tolerance of the
mean radius of the last three readings of 0.08 to 0.1 is exceeded
(dependent on n), the " Evaluation!" message will
appear on the screen.
- In this case, check the tear film of the eye being examined, ask the
patient to blink if necessary and repeat the measurements until the
results are within the tolerances. The Evaluation! message will then
- The measuring errors must be deleted if necessary, as the readings
obtained in the Evaluation! state will not be accepted for ACD
measurement, IOL calculation and the database for optimization of
- Highlight the reading to be used for IOL calculation: By default, the
last reading will be highlighted in blue.
To obtain consistent results we recommend checking
the individual keratometer measurements.
Carry out further measurements if