Alignment system for ophthalmic instrument

A method of aligning an ophthalmic instrument with respect to a centre of a cornea of an eye, comprising the steps of:

• a) directing a beam of light from the ophthalmic instrument to the cornea of the eye along a direction of an optical axis of the eye;
• b) taking, at a plurality of locations around the beam using at least three photodiodes, measurements of intensity of the light reflected from the cornea of the eye;
• c) determining the position of the ophthalmic instrument relative to the eye from the measurements of intensity of the light reflected from the cornea of the eye in three spatial axes;
• d) moving the ophthalmic instrument relative to the eye from the determined position to a desired position in the three spatial axes, wherein the desired position is a position that equalizes the measurements of the intensity of the light reflected from the cornea of the eye taken at a plurality of locations around the beam using the at least three photodiodes.