Carl Zeiss Gmbh

Barry T Kavoussi

Ming Lai

Christopher J R V Baker

Method and apparatus is disclosed for mapping a corneal contour and thickness profile. In accordance with one aspect of the present invention, a set of narrow, collimated, parallel beams is projected onto a corneal surface at an angle with respect to a predetermined axis (&ldquo;an instrument axis&rdquo;) that is substantially aligned with a visual axis of an eye. The set of beams is rotated about the instrument axis. A CCD camera is disposed to view the cornea along the instrument axis. Traces of the rotating set of beams form a set of rings in images obtained by the CCD camera; wherein outer and inner edges of the rings correspond to intersections of the set of beams with anterior and posterior surfaces of the cornea, respectively. Next, a direct triangulation algorithm is used to determine spatial positions of data points along the outer edges of the rings, and these spatial positions are used to reconstruct the anterior surface profile of the cornea. Next, using the anterior surface profile of the cornea, a ray tracing triangulation algorithm is used to determine spatial positions of data points along the inner edges of the rings, and these spatial positions are used to reconstruct the posterior surface profile of the cornea. Finally, spatial differences between the posterior and anterior surface profiles of the cornea provide the thickness profile.

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Danville, CA, United States of America

Barry T Kavoussi