The use of the classical keratometric approach with a single value of nk in keratoconus for the calculation of IOL power is inaccurate and may be the reason for some refractive surprises in this type of eyes after cataract surgery.
This inaccuracy can be minimised by using an adjusted keratometric approach based on the estimation of the keratometric corneal power, using a variable nk depending on the radius of curvature of the anterior corneal surface, with a maximum error in most of cases of approximately 0.6 D and over 1 D in very few cases.
We have conducted a successful preliminary clinical validation of this approach for IOL power calculation, and a clinical validation with a larger sample size including severe keratoconus cases is now necessary so that more consistent conclusions can be obtained.
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