Carl Zeiss Meditec IOL Master
IOLMaster — Keratometer Tips.
Ask the patient to relax and look at the yellow fixation light. If the patient cannot see the fixation light, he or she should look straight ahead into the IOLMaster.
When aligning the IOLMaster, make sure that all the 6 peripheral points are visible and located in the field between the two auxiliary circles, as closely as possible to the center of the display. The images of the measuring marks on the display must be optimally focused by varying the distance between patient and device. The images of the measuring marks should be circular or ellipsoid.
Remember to place a drop of artificial tears in each eye, have the patient blink several times, and do all measurements with both eyes open as WIDE as possible. This will improve the reflectivity of the cornea. A reminder message will appear below the video image when you activate the keratometer mode.
The "Error" message may have two basic causes:
The images of the measuring marks are too large due to the IOLMaster being defocused. The system cannot calculate a measured value and "Error" appears in the display field.
After correcting the focus adjustment to minimize the peripheral mark size, the measurement can be retaken (old value will be automatically overwritten). Sometimes, with exactly adjusted focus, small circles (like haloes) may be visible around the six peripheral measuring points. In this case, focusing is optimal.
Missing Measuring Marks
The display field shows the "Error" message. This error may also occur, if the patient blinks his or her eye during the measurement (0.5s). This may happen particularly with noncompliant or anxious patients.
Ask the patient to open his or her eyes WIDE and repeat the measurement. If this does not resolve the problem, carefully pull up the upper eyelid without indenting the globe.
In the measurement of pseudophakic eyes, it may happen that images produced at the front side of the intraocular lens are visible next to the reflections from the cornea.
These reflections from the IOL are fainter and out of focus.
Move the IOLMaster approximately 1 mm away from the patient's eye (defocusing) and take the measurement. The images produced at the cornea will now be slightly larger, while the artifacts of the IOL become fainter, such that the evaluation process may not identify the IOL reflection as measuring points. The measurement is then possible. If this procedure does not succeed, the corneal curvature cannot be measured.
If the tear film is suddenly interrupted, the reflectivity of the cornea will be greatly reduced at these points and the cornea will scatter the light more strongly. If a measuring mark is projected to such a region, the otherwise circular or ellipsoid image of the measuring mark will become irregular. You will see irregular marks and/or multiple reflections. In this case, a precise measurement of the corneal curvature will not be possible. The results will fluctuate or the "Error" message will be displayed.
Place a drop of artificial tears in each eye, have the patient blink several times, and do all measurements with both eyes open as WIDE as possible. Take the measurement immediately.
Irregularities of the Corneal Surface (Scars)
Scars and local irregularities on the corneal surface impair the imaging quality of the measuring marks. Depending on the expansion and location of these irregularities, measuring errors may arise.
Try to position the measuring mark next to, above or below the scar by slightly displacing the IOLMaster relative to the eye. Then, take the measurement. In such cases, it is advisable to repeat the measurement several times. Depending on the degree of irregularity, fluctuations or measuring errors may occur.