Treatment apparatus for operatively correcting defective vision of an eye, method for generating control data therefor, and method for operatively correcting defective vision of an eye
A treatment apparatus for operatively correcting myopia or hyperopia in an eye includes a laser device controlled by a control device and that separates the corneal tissue by applying a laser beam. The control device controls the laser device to emit the laser beam into the cornea such that a lenticule-shaped volume is isolated in the cornea. The control device, when controlling the laser device, predefines the lenticule-shaped volume such that the volume has a minimum thickness of between 5 and 50 μm. For myopia correction, the minimum thickness occurs on the edge of the volume, and for hyperopia correction the minimum thickness occurs in the region of the visual axis.
1. A treatment apparatus for surgical correction of defective vision of an eye, the treatment apparatus comprising:
a laser device including a laser, optics and a 3D focus shifting device, wherein the laser device is controlled by a control device and separates corneal tissue of the eye by applying laser radiation;
the control device being programmed with an algorithm that controls an operation of the laser device to emit the laser radiation into the cornea at different focus positions wherein the controlled operation of the laser device isolates a lenticular shaped volume in the cornea, the lenticular volume being structured such that removal of the volume effects a correction of the defective vision; and
the control device being programmed with the algorithm that controls the operation of the laser device such that the lenticular volume has a curved posterior face, an anterior face and a zone of transition between the posterior face and the anterior face, wherein the zone of transition has, in a view along the optical axis, a width which is larger than a width of a hypothetical edge cut which is uncurved and which extends perpendicular from a first edge of the anterior face to a second edge of the posterior face.
2. The apparatus according to claim 1 , wherein the zone of transition has a width of at least 0.1 mm.
3. The apparatus according to claim 1 , wherein the zone of transition has a first portion which is uncurved and connects to the anterior face at an angle of 80° to 100° to a viewing axis of the eye or perpendicularly.
4. The apparatus according to claim 3 , wherein the zone of transition has a second portion which connects to the first section and which is curved.
5. The apparatus according to claim 4 , wherein the second portion is concavely curved relative to the lenticular volume, thereby making an indentation to the lenticular volume.
6. The apparatus according to claim 3 , wherein the zone of transition has a second portion which is uncurved and inclined more acutely toward the axis of vision that the first section.
7. The apparatus according to claim 3 , wherein the first portion has a height d R selected from a group consisting of more than 5 μm and at least 10 μm.
8. The apparatus according to claim 3 , wherein the defective vision comprises hyperopia and the first portion has a height d R defining a minimum thickness d M of the lenticular volume at the viewing axis.
9. The apparatus according to claim 1 , wherein the zone of transition is located outside an area corresponding to a scotopic pupil of the eye.
10. The apparatus according to claim 1 , wherein the zone of transition provides the lenticular shaped volume with an edge thickness of not more than 10 μm.
11. The apparatus according to claim 1 , wherein the zone of transition provides for an edge face which forms with a plane in which the axis of vision is contained a cut curve,
wherein the cut curve has an extension that is, when seen perpendicular to the viewing axis, larger than an extension of one of the following two hypothetical lines:
a straight line extending perpendicularly from the border of the posterior face to the anterior face or to an imaginary continuation thereof,
a straight line extending perpendicularly from the border of the anterior face to the posterior face or to an imaginary continuation thereof.
12. The apparatus according to claim 1 , wherein
the control device further is programmed with the algorithm that controls the laser device such that the anterior face is positioned at a constant distance d F from the anterior surface of the cornea and the posterior face is curved and has a radius of curvature R L =R cv *−d F , wherein R CV * satisfies the following equation
R CV *=1/((1/ R CV )+ B BR /(( n c −1)·(1− D HS ·B BR )))+ F,
and R CV is a radius of curvature of the cornea before removal of the volume, n c is a refractive index of a material of the cornea, F is a correction factor, B BR is a refractive power of a pair of spectacles suitable for correcting defective vision, and also d HS is a distance at which the pair of spectacles having the refractive power B BR would have to be positioned before a corneal apex in order to achieve a desired correction of defective vision by the pair of spectacles.
13. The apparatus according to claim 12 , wherein the control device further is programmed with the algorithm that controls the laser device such that the following applies
F =(1−1/ n c )·( d C *−d C ),
wherein d C and d C * respectively denote a thickness of the cornea before and after removal of the volume and the radius R CV * can be calculated iteratively in that during each iteration step a change in thickness (d C *−d C ) is concluded from the difference (R CV *−R CV ) and the corresponding result obtained therefrom for the change in thickness is applied in the calculation of R CV * in a next iteration step.
14. The apparatus according to claim 1 , wherein the control device is programmed such that a single one of the following applies:
the defective vision comprises myopia and the lenticular volume has a minimum thickness d M in a range of from 5 to 50 μm at a peripheral edge of the lenticular volume and
the defective vision comprises hyperopia and the lenticular volume has a minimum thickness d M in a range of from 5 to 50 μm at or near an axis of vision of the eye.
15. The apparatus according to claim 14 , wherein the anterior face is in a constant distance d F from the anterior surface of the cornea and the posterior face satisfies the equation
z L ( r ,φ)= R L (φ)−( R L 2 (φ)− r 2 ) 1/2 +d L +d F
in cylindrical coordinates (z, r, (p), the origin of which is positioned at the point at which the axis of vision passes through the front face of the cornea.
16. The apparatus according to claim 1 , wherein a peripheral end of the zone of transition presents an angle relative to the anterior face.
17. The apparatus according to claim 1 , wherein a peripheral end of the zone of transition presents an acute angle relative to the anterior face.
18. A method for surgical correction of defective vision of an eye, the method comprising:
isolating a lenticular shaped volume in the cornea by emitting laser radiation into a cornea at different focus positions, the lenticular volume being structured such that removal of the volume effects a correction of the defective vision;
wherein the lenticular volume has a curved posterior face, an anterior face and a zone of transition between the posterior face and the anterior face, wherein the zone of transition has, in a view along an optical axis, a width which is larger than a width of a hypothetical edge cut which is uncurved and which extends perpendicular from a first edge of the anterior face to a second edge of the posterior face.
19. The method according to claim 18 , wherein the zone of transition has a width of at least 0.1 mm.
20. The method according to claim 18 , wherein the zone of transition has a first portion which is uncurved and connects to the anterior face at an angle of 80° to 100° to a viewing axis of the eye or perpendicularly.