Systems, methods and apparatus for performing selective ablation of a
corneal surface of an eye to effect a desired corneal shape, particularly
for correcting a hyperopic/astigmatic condition by laser sculpting the
corneal surface to increase its curvature. In one aspect of the
invention, a method includes the steps of directing a laser beam onto a
corneal surface of an eye, and changing the corneal surface from an
initial curvature having hyperopic and astigmatic optical properties to a
subsequent curvature having correctively improved optical properties.
Thus, the curvature of the anterior corneal surface is increased to
correct hyperopia, while cylindrical volumetric sculpting of the corneal
tissue is performed to correct the astigmatism. The hyperopic and
astigmatic corrections are preferably performed by establishing an
optical correction zone on the anterior corneal surface of the eye, and
directing a laser beam through a variable aperture element designed to
produce a rectangular ablation (i.e., cylindrical correction) on a
portion of the optical correction zone. The laser beam is then displaced
by selected amounts across the optical correction zone to produce a
series of rectangular ablations on the correction zone that increases the
curvature of the corneal surface to correct the hyperopic refractive
error.