Carl Zeiss Meditec IOL Master
Cataract Surgery Arizona

IOLMaster — Keratometer Measurements.

IOLMaster Arizona   IMPORTANT: 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 <K> key
  • pressing the <SPACE BAR> in ALM mode (ALM)

2. Tell the patient to focus on the yellow light Cataract Surgery Arizona.

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.

IOLMaster Arizona   Note
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 measurement.
  IOLMaster Keratometer

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.

IOLMaster Keratometer  

The size and shape of measurement points are verified by the software. If a measurement point is not correctly identified, a blue flashing dot will appear.

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 precaution.

Keratometer measurements may be repeated as often as desired; however, only the last three measurements will be displayed.

IOLMaster Arizona   Note
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 <CTR> + <Z> (UNDO function is irrevocable). To delete one of the three displayed readings, select it and press the <DEL> key. Now confirm with YES.

IOLMaster Keratometer

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 disappear.
  • 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 constants.
  • Highlight the reading to be used for IOL calculation: By default, the last reading will be highlighted in blue.
IOL Master warning WARNING: To obtain consistent results we recommend checking the individual keratometer measurements. Carry out further measurements if necessary.


Be sure to read: Tips for Keratometer