In this segment of the Spotlight on Cataracts: Clinical Decision-Making with Cataract Complications series from the 2012 Annual Meeting, Dr. Douglas Koch briefly reviews the art of IOL calculation — the traditional extrapolation methods for determining effective lens position (ELP) — then reports some encouraging results of developing scientific methods to measure corneal refractive power accurately, determine correct IOL power intraoperatively, and adjust IOL power postoperatively.