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000000Ć1150Ć839 IOLMaster 11.02.2004
Interpretation of axial length measurements
As a rule, an interference signal is produced if the measuring light is
reflected by the tear film and the retinal pigmented epithelium of the
eye. This signal is utilized for axial length measurements.
Note:
Ultrasonic biometrical instruments measure the axial length as
that distance between the cornea and the inner limiting
membrane because the sound waves are reflected at this
membrane. To ensure that the measured values obtained with
the IOLMaster are compatible with those obtained through
acoustic axial length measurement, the system automatically adĆ
justs for the distance difference between the inner limiting
membrane and the pigmented epithelium. The displayed axial
length values are thus directly comparable to those obtained by
immersion ultrasound!
It is absolutely necessary
to reĆpersonalize the "lens constants"
for use with the IOLMaster prior to applying it's calculation values
to determine lens power and surgical technique. Refer to the
specialist literature and the publications of the authors of the IOL
formulas regarding the personalization of constants (Surgeon
Factors).
Updated information is available on the Internet at:
http://www.meditec.zeiss.com/iol_master
and/or
http://www.augenklinik.uniĆwuerzburg.de/eulib/
With an optimally aligned instrument, a good SNR and weak ametropia
(approx.
v
6 D), the secondary maxima located symmetrically on each
side of the measuring peak will be seen (Fig. 48).
These maxima are an artefact of the light source.
The distance from each of the secondary maxima to the peak signal is
approximately 0.8 mm. The secondary maxima are likewise always
visible in measurements of the provided test eye.
Fig. 48 Undisturbed measuring
signal with secondary
maximaĄ
Evaluation of ALM results
