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Carl Zeiss Meditec IOL Master
Cataract Surgery Arizona

IOLMaster — White-to-White Measurement (WTW).

^IOLMaster W KEY

Determination of "White-to-White" (optional)

  • Activate the WTW mode by:

    • clicking on the WTW icon
    • pressing the <W> key
    • pressing the <SPACE BAR> in ACD mode (ACD)
  • The patient should look at the yellow fixation light yellow light in the center.
  • Align the IOLMaster so that the six peripheral measuring points are symmetrical to the cross-hair and the iris structures or the edge of the pupil appears optimally focused.

    The fixation point in the center of the 6 light dots is usually not in the center of the pupil or iris, because only in the rarest cases does the visual axis correspond to the optical axis of the eye.

IOL Master warning WARNING: Ask the patient if he or she sees the fixation point. If the patient fails to fixate properly, the visual axis will not be correctly detected, which may result in measuring errors.
  • Take the measurement by pressing the button on the joystick.
IOLMaster white to white measurement

Each time the joystick button is pressed, an image of the eye is displayed in which the detected iris edge is marked. After a check of correct recognition of the iris and the fixed point has been performed, confirm with OK. Only then is the data valid and available for further processing.

IOL Master warning WARNING: The validity of the WTW determination depends on this check of correct recognition of the iris edge.

The WTW value is the horizontal diameter of the iris. In addition to the WTW value, the distance of the visual axis from the center of the iris (x, y) will also be displayed.

The values are stated in millimeters with reference to a Cartesian coordinate system, the zero point of which is assumed to be in the established center of the iris or pupil. If the visual axis is above the iris or pupil center, the Y value will be positive; if it is below, the value will be negative. X values to the left of the center are negative; those to the right are positive.

IOLMaster Arizona   Note
If the software has difficulty detecting the iris or fixation point, this may be due to inadequate room lighting. It is recommended that the front panel and examined eye be shielded from direct or lateral light. The best results will be obtained when the examination room is slightly darkened.

WTW measurement may be repeated as often as desired.

Measurement of Other Eye

The system automatically registers which eye is being measured (OD or OS). All past readings of this patient are still stored and may be retrieved as necessary. Measurements of the other eye must be performed analogously to the previous eye.

IOLMaster Arizona   Note
After each change of side, the overview mode is automatically activated for coarse alignment.

Proper Adjustment of IOLMaster

Ask the patient to relax and look at the yellow fixation light yellow light.

Focus on the iris, not on the illuminated dots. Adequate room lighting will facilitate the detection of iris structures. Avoid direct exposure of the eye and device front panel to extraneous light.

In particular, ensure that the visible right and left edge of the iris is not disturbed by reflections from lamps and windows.

If the iris structure is not discernible, focus on the edge of either iris or pupil.

Serious defocusing will result in incorrect data.

After the image has been taken, the operator should check if the software has correctly detected the edge of the iris. If the circle segments drawn in the image do not define the iris correctly, the result must be discarded. Click on OK to confirm the results and save the data.