The present invention relates to an apparatus and a method for measuring a displacement in vivo in situ of an eye, along with a method of assessing of an eye condition. More particularly, the apparatus and method of the present invention permits measurements of a displacement of at least two points in proximity of an optic disc, in the eye of a patient. For doing so, the apparatus uses a probing unit, an analog/digital converter and an analyzer. The displacement measured may include a pulsatile displacement of the lamina cribrosa, so as to perform early assessment of an eye condition.