A laser-based method and apparatus for corneal and intraocular surgery. The preferred method of performing a surface ablation of cornea tissue or other organic materials uses a laser source which has the characteristics of providing a shallow ablation depth or region (about 0.2 .mu.m to about 5.0 .mu.m), a low ablation energy density threshold (about 0.2 to 5 .mu.J/(10 .mu.m).sup.2), and extremely short laser pulses (having a duration of about 0.01 picoseconds to about 2 picoseconds per pulse) to achieve precise control of tissue removal. The laser beam cross-sectional area is preferably about 10 .mu.m in diameter. The preferred laser system includes a broad gain bandwidth laser, such as Ti.sub.3 Al.sub.2 O.sub.3, Cr:LiSrAlF.sub.6, Nd:YLF, or similar lasers, with a preferred wavelength of about 830 nm, which is generally transmissive in eye tissue. Various surgical procedures can be performed to correct refractive errors or to treat eye diseases. The invention can be used to excise or photoablate regions within the cornea, capsule, lens, vitreoretinal membrane, and other structures within the eye. The invention provides an improved method of eye surgery which has accurate control of tissue removal, flexibility of ablating tissue at any desired location with predetermined ablation depth, an optically smooth finished surface after the surgery, and a gentle surgical beam for laser ablation action.
An ophthalmic applanator for treatment of corneal lamellar flaps/caps includes a disc having a concave bottom surface with a curvature flatter than the curvature of the external surface of the cornea of the eye and steeper than the curvature of the surface of the sclera of an eye and a concave or convex top surface. The radius of curvature of the bottom surface produces a radiating pressure of higher magnitude centrally than peripherally, but is also curved sufficiently to minimize the risk of excessive indentation of the cornea. The convex or concave upper surface reduces reflection from the operating microscope.
A method for separating lamellae in the stroma of an eye includes establishing a focal depth that will be located in relatively weaker tissue at an interface layer between lamellae in the stroma. A laser beam can then be focused to photoablate stromal tissue and create a photoablative response thereto. This photoablative response is then compared to a reference value using wavefront analysis techniques to determine an effective minimum energy level for the laser beam. Maintenance of a proper focal depth can be periodically verified by maintaining a birefringent reference using an ellipsometer. Once the lamellae are separated, a flap of corneal tissue can be created that can be lifted to expose underlying stromal tissue for further surgical photoablation.
A laser system serves for corneal grafting by photodisruptive laser cutting. To this end, short laser pulses within the range from 1 fs to 10 ns are positioned and guided in the cornea in such a way that the foci (20) of the laser pulses describe an incision path in the cornea (12) that exhibits an undercut, so that a seal between the juxtaposed surfaces of the implant and of the residual cornea arises between a donor implant and the recipient cornea which is promoted by the overpressure of the eye
A device and method for increasing the accuracy of an ocular laser procedure by detecting and compensating for small eye movements includes the establishment of a corneal reference plane. To create the corneal reference plane, a laser beam is first used to photoablate stromal tissue at three different locations in the cornea. Bubbles that are created upon photoablation define the plane and can be imaged to determine the position of the plane as the eye moves. A pair of cameras and a processor are provided to image the cornea and triangulate the position of the reference plane. The updated position of the corneal reference plane is then used to guide the path of the laser beam during the course of the ocular procedure.
A process for monitoring and controlling the adjustment of treatment parameters in an ophthalmic treatment device which comprises a radiation source generating at least a treatment beam and, optionally, a target beam and an applicator which is connected with the radiation source via at least one optical element and can be attached to a slip lamp, wherein the following steps are provided: a) the irradiation parameters such as intensity, magnification of the contact lens placed on the eye, radiation dose per unit area, and spot size on the retina are adjusted by the operator at the radiation source; b) first parameters to be adjusted at the applicator are calculated on the basis of patient-related influencing variables such as contact lens magnification and the size of the spot to be realized on the retina, so that a determined spot size and intensity of the treatment beam to be applied can be realized at the treatment site on the retina; and c) parameters adjusted at the applicator are compared with the first parameters by means of a computer and the adjusted parameters are made to coincide with the first parameters representing reference values, and the parameters serving as reference values are realized and maintained constant for the duration of irradiation. An arrangement for carrying out the process employing an ophthalmic treatment device is also disclosed.
