 Standard keratometry measures an intermediate area and extrapolates the central power based on some very broad assumptions. For this reason, keratometry, autokeratometry and simulated keratometry by topography will typically over-estimate central corneal power following keratorefractive surgery for myopia. This inaccuracy leads to an inability to meet the patients rising expectations and with the increasing popularity of refractive surgery, calculating intraocular lens IOL power after refractive surgery is becoming increasingly important. 