Method and device for cornea reshaping by intrastromal tissue removal
View Patent ↗A method and device for flapless, intrastromal keratomileusis for the correction of myopia, hyperopia and astigmatism, i.e., for vision correction by corneal reshaping without creating a flap. Ultra-short laser pulses are used to create a temporary micro-channel extending to an end point located within the cornea. A second series of ultra-short laser pulses are then delivered to photo-ablate material in the vicinity of the micro-channel end-point. The photo-ablated material may exit through the micro-channel used to deliver the laser pulses, or via a separate micro-channel. With the micro-channel oriented substantially normal to the optical axis of the cornea, and by continuing to supply the ultra-short laser pulses in the appropriate number while moving the point of ablation along the micro-channel, the photo-ablation of the intrastromal tissue may continue in a controlled fashion and the cornea reshaped in a predetermined manner without creating a flap.
1. A method for removing material from an interior portion of a cornea without creating a flap, said method comprising the steps of:
creating a temporary micro-channel extending from a surface of said cornea to a micro-channel end point located within said cornea by delivering a first plurality of ultra-short laser pulses; and
multi photon ablating material in a vicinity of said micro-channel end point by delivering a second plurality of ultra-short laser pulses with pulse energies of 20 μJ or greater and focused down to a pulse intensity between a range of 10 13 to 10 15 W/cm 2 .
2. The method of claim 1 wherein said micro-channel is oriented substantially normal to the optical axis of said cornea.
3. The method of claim 2 wherein said first plurality of ultra-short laser pulses forming said micro-channel are delivered in a first window of time, are directed substantially normal to the optical axis of said cornea, have a pulse duration of 500 femtoseconds or less, have a pulse energy of 5 mJ or less, have a repetition rate of 1 kHz or greater and are focused down to a diameter of between 50 and 100 μm, and wherein said second plurality of ultra-short laser pulses is are delivered in a second window of time.
4. The method of claim 3 wherein each pulse of said second plurality of ultra-short laser pulses is directed substantially normal to said optical axis, and wherein said multi-photon ablating creates an over-pressure within the ablated area of the cornea causing an outflow of said ablated material in the form of a gas or liquid via said micro-channel.