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Frequently Asked Questions 8-5
steeper than manual K’s, while on a post-refractive eye, the IOLMaster K’s may
be slightly flatter.
IOLMaster K’s
Manual K’s
Second, the IOLMaster determines curvature by measuring the relative position
of six spots on the cornea, rather than the two mires of manual keratometry,
thus providing more detail.
Third, if your IOLMaster is set to give curvature results in diopters rather than
radius, the original radius is converted into diopters using the keratometry
refractive index of 1.3375, which is not the same value as some other keratometry systems use.
The joystick controls seem so touchy. Is it broken?
Probably not. When you are performing a test, your screen is zoomed in very
close to the patient’s pupil, so even a little movement of the controls has a big
impact on the pupil position. So be sure to hold the joystick firmly with one
hand and the base of the scanner (just beside the joystick) with the other, and
move the scanner using both hands together.
Do I do anything different when measuring a pseudophakic patient?
Yes, in two ways:
1. When in Axial Length Mode, select the appropriate pseudophakic IOL type
from the AL Settings menu at the top of the screen. This must be done before
calculating the IOL for that patient but not before measuring the patient.
Please see What About Eyes That Have Already Had Surgery? (page
4-12) for more details about this.
2. Be cautious when measuring axial length on a pseudophakic patient. You will
sometimes get two tall spikes, one unusually short and one at the axial length
you would expect for that patient. The first unusually short spike is probably
the instrument picking up a reflection from the IOL that is in the patient’s eye.
If this spike is equal or taller than the more “realistic” axial length, the
IOLMaster: A Practical Operation Guide