Methods for IOL calculations for Cataract Surgery after prior LASIK

The three main factors in IOL calculations are corneal power, axial length, and effective lens position. Prior LASIK makes this more challenging because it will affect the corneal power, making dioptric measurements more challenging. The prior LASIK may also affect the calculation of the effect lens position (ELP) since some formulae will use the keratometry value in determining ELP.
IOL calculations are, in fact, estimations and this is particularly true in eyes with prior kerato-refractive surgery such as LASIK. We can get reasonably close to achieving our post-op goal of plano for this patient, but the spread of the results bell curve is wider than for virgin eyes.

[@PUMBAZZ]

I've always been thought: Myopic LASIK=overestimation of corneal power, subestimation of iol power. What I never understood is: if we made the cornea flat with a laser, why do we overestimate the corneal power?

[@UdayDevgan]

Most keratometers measure the cornea power at the edge of a 3 mm optical zone but the true corneal power is lower in the center of the cornea after myopic lasik. Also most devices just measure the anterior corneal and assume a normal anterior:posterior ratio. For example a K of 44 would actually mean an anterior power of 50 and a posterior power of -6 diopters. Lasik will just change the anterior curvature of the cornea and not affect the posterior corneal power.

[@PUMBAZZ]

@@UdayDevgan Thank you! it's crystal clear now!

[@UdayDevgan]

Derrick A. Dabian check out CataractCoach.com for much more great material

[@PUMBAZZ]

@@UdayDevgan #1 Fan, thank you for all you do for us residents!