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000000Ć1150Ć839 IOLMaster 11.02.2004
As the change in refraction was achieved by the variation of the corneal
refraction, the currently effective corneal refraction directly results from
the difference between preoperative and postoperative refraction,
corrected by the corneal vertex distance (vertex correction). The
computational method is described in technical literature. If the
corresponding data of the patient are available, the Refractive History
Method delivers the most accurate results.
With the
Contact Lens Method
(contact lens overrefraction), one tries
to determine the currently effective corneal refraction by two refraction
measurements, once with and once without hard 'plane' contact lens.
The following parameters are needed:
q
Refraction with contact lens,
q
Refraction without contact lens,
q
Refractive power of the (plane or almost plane) hard contact lens ć
refractive power of contact lens back surface and
q
Corneal vertex distance.
In the ideal case, the refractive power of the contact lens back surface
is equal to the unknown corneal refraction. From that point of view,
several hard plane contact lenses with refractions of the back surface
between 30 and 45 D should be available.
For the calculation of the corneal refraction, enter the necessary data
of the patient in the data mask on the screen.
Fig. 26 Correction of corneal refraction
For the calculation of the IOL, the Corneal K's selected by the examiner
with <Apply> will be transferred to the IOL calculation table. On
selection of the biometric formula, you can start IOL calculation.
Operation
