The Camellin - Calossi formula

Nowadays is well stated that after keratorefractive surgery, without a special correction, the intraocular lens (IOL) power is usually inaccurate. The article by Kenneth J. Hoffer1 which appeared in the first JanuaryMarch 2010 issue of the Journal of Emmetropia is an excellent review of recently published studies that analyze and try to solve the problems to calculate IOL power in eyes with prior refractive surgery. In his review, Hoffer report our method2 as a mere correction factor to the keratometric index of refraction. This is not true. The reason why the IOL power after corneal refractive surgery could be inaccurate is multifactorial. The possible sources of error are: change of corneal asphericity, change of ratio between anterior and posterior corneal surfaces, and K-based estimation of effective lens position. For this reason, we proposed a formula based on a multiple approach2-4. Our formula originates from a theoretical one that we empirically adjusted in two parameters: 1) the corneal power and 2) the prediction of effective lens position: