We present the difficulties in choosing the right IOL, when facing a great variability of the keratometric measurements, in the case of a patient operated for epiretinal membrane and lamellar macular hole, who developed complicated cataract in the operated eye. Upon commencing the biometric measurements, inconsistency in keratometric values led to further investigations. Repeated placido disc topography initially showed corneal ectasia, which posed a problem on selecting the right type of intra-ocular lens. Ocular surface pathology was suspected, and after treatment, the topography was repeated with a Scheimpflug topographer, that showed an improved keratometric profile. The surgical solution was to implant an aspheric monofocal IOL, in the bag, with extended depth of focus that enhances intermediate vision, disregarding the previous keratometric measurements. Refractive and functional outcomes were good. In cases of biometric measurements that show inconsistency in keratometric values, ocular surface disease as well as corneal ectasia should be taken into consideration. The right implant should not be chosen based on a single measurement, but rather several measurements should be made and compared and the choice should not be made before treating the ocular surface.