Minimizing the side-effects of refractive corrections using statistically determined irregularities in intrastromal incisions
View Patent ↗A system and method for minimizing adverse visual effects that may be introduced during laser refractive surgery, requires making laser incisions into stromal tissue in a predetermined manner. Specifically, a plurality of irregular incisions are statistically distributed in the stroma in a manner that causes them to be visually elusive, and thereby minimize their adverse visual effects. The incisions must, however, still accomplish their intended surgical purpose of weakening the stroma in a predetermined manner. To do this, each irregular incision has a width of arc length dθ m , a length dz l and a characteristic radial distance dr n from the visual axis of the eye. Values for dθ m , dz l and dr n are established using a random number generator.
1. A method for minimizing visual side-effects of a refractive surgical procedure which comprises the steps of:
identifying a change for biomechanical stresses within a stroma of an eye, wherein the change is necessary to affect a defined optical correction;
determining a statistical distribution for structural alterations in the stroma to implement the change;
creating a plurality of unique irregular incisions manifesting the structural alterations in the stroma to accomplish the optical correction;
locating each irregular incision in accordance with the statistical distribution to cause the plurality of irregular incisions to become visually elusive for minimizing the visual side-effects of the surgical procedure while achieving the defined optical correction; and
wherein the eye defines a visual axis and has an anterior surface, and wherein each irregular incision is defined by a length dz l measured along a line perpendicular to the anterior surface and by an arc width dθ m measured along an azimuthal arc centered on the visual axis, and further wherein each irregular incision is located at a radial distance dr n from the visual axis.
2. A method as recited in claim 1 wherein each arc width dθ m is in a range between approximately 8° and 12°, wherein m =1→36, and wherein Σdθ m =360°.
3. A method as recited in claim 2 wherein each irregular incision having a same dθ m has a same dz l +an overlap Δ, wherein l=1→10, wherein each dz l is in a range of 30 μm to 50 μm, and further wherein Δ<approximately 10 μm.
4. A method as recited in claim 3 wherein each irregular incision having a same dθ m is located by said radial distance dr n , wherein n=1→5, dr 1 >1 mm and Σdr n <approximately 2 mm.
5. A method as recited in claim 4 wherein the distance dr n for an irregular incision in a dθ m is established to be within a respective predetermined radial distance of other irregular incisions with a same dr n in dθ m+1 and in dθ m−1 .
6. A method as recited in claim 4 wherein the distance between dr n and dr n+1 within a same dθ m is greater than approximately 50 μm.
7. A method as recited in claim 4 wherein values for dθ m , dz l and dr n are established by using a random number generator.
8. A method as recited in claim 4 wherein dr n is a radial extension of dr n+1 .
9. A method as recited in claim 1 wherein the irregular incisions of dθ m are axially symmetric with the irregular incision of dθ m +180°.
10. A method for creating a pattern of irregular incisions in the stroma of an eye to correct a vision defect, with minimal resulting visual side effects, the method comprising the steps of:
defining each irregular incision in the pattern relative to a geometry of the eye, wherein the eye geometry includes a visual axis and an anterior surface, and each irregular incision has an arc width dθ m measured along an azimuthal arc centered on the visual axis, with a length dz l plus an overlap Δ measured along a line substantially perpendicular to the anterior surface of the eye;
locating each irregular incision within a same dθ m using a characteristic radial distance dr n ; and
using a random number generator to establish values for dθ m , dz l and dr n .
11. A method as recited in claim 10 wherein each arc width dθ m is in a range between approximately 8° and 12°, where m =1→36 and Σdθ m =360°, wherein l=1→10 and each dz l is in a range of 30 μm to 50 μm with Δless than approximately 10 μm, and further wherein n =1→5 with dr 1 greater than approximately 1 mm and Σdr n less than approximately 2 mm.
12. A method as recited in claim 10 wherein dr n and dz l of dθ m is the same as the respective dr n and dz l of dθ m +180°.
13. A method as recited in claim 12 wherein m=1→18 and Σdθ m =180°.
14. A method as recited in claim 10 wherein the distance dr n for an irregular incision in a dθ m is established to be within a respective predetermined radial distance of other irregular incisions with a same dr n in dθ m+1 and in dθ m−1 .
15. A method as recited in claim 14 wherein the distance between dr n and dr n+1 within a same dθ m is greater than approximately 50 μm.