A modified slit lamp is described which makes axial eye length measurements with optical interferometry available to the clinic. A separate partial coherence Doppler interferometer is coupled to the slit lamp optics by a monomode fiber and a slit lamp attachment. As compared with the more common ultrasonic echo-impulse technique the main advantages of this technique are its high accuracy and resolution and its noncontact operation. The instrument is described and first results are presented. A standard deviation of +/- 21 micrometers has been obtained.