An interferometric axial eye length measurement apparatus having a light source adapted to produce a beam of partially coherent light, a first mirror and a second mirror disposed in the reference arm, and a processor adapted to control at least the second mirror such that a corneal interference peak and a second interference peak have a non-zero separation. There is at least one variable delay optical element having a delay signal, wherein the delay signal corresponding to a region between the corneal interference peak and second interference peak is substantially linear.