In certain embodiments calculating intraocular lens (IOL) power includes determining locations of parts of an eye along an axis of the eye. The locations include the location of a cornea the anterior and posterior locations of a crystalline lens and the location of a retina. An IOL location of an IOL is calculated according to the anterior and posterior locations of the crystalline lens. Corneal data is also determined. The IOL power is calculated using the corneal data the IOL location and the retinal location. In certain embodiments refractive indices are determined for segments of the axis and at least one location is adjusted according to the refractive indices.
