Method of locating the visual axis objectively.

Purpose To locate the visual axis of the eye objectively. Method Based on three-beam scanning laser radar microprofilometry, a technique is proposed to objectively locate the visual axis of the eye. The laser beam consists of three components, two of them being shifted relatively to the central one by differing frequencies, filtered in spatially orthogonal directions. The centre of the foveola is defined as the crossing of steepest inclinations determined in the specific beam positions on the trajectory of scanning. The position of the cornea crossing by the visual axis is designated by the optical axis of the measuring instrument. Results Nanometer sensitivity was confirmed in a preliminary test. Conclusions The proposed technique can be incorporated into any clinical wavefront sensing instrument and can be used for centration-sensitive vision correction, as well as for other instances when knowing the exact position of the fovea is important. [ABSTRACT FROM AUTHOR]