Excimer laser unit and relative control method for performing cornea ablation to reduce presbyopia

1. A method of controlling an excimer laser unit to perform cornea ablation to reduce presbyopia, the method comprising the step of:

a) controlling said excimer laser unit to produce on the cornea a photoablative pattern inducing a fourth-order ocular aberration;

wherein said induced fourth-order aberration is a spherical aberration; and

wherein said step a) further comprises the steps of:

a1) acquiring and interpreting an aberrometric map of the eye indicating the visual defects of the eye, said visual defects comprising second-order visual defects including hypermetropia, astigmatism, and myopia, and higher-order visual defects including spherical aberration, thereby detecting a fourth-order spherical aberration;

a2) if the detected spherical aberration is negative, supplying said excimer laser unit with an overcorrect photoablative pattern that results in an induced fourth-order positive spherical aberration after treatment, the overcorrect photoablative pattern being obtained by obtaining a photoablative pattern to correct a fourth-order spherical aberration that is increased numerically in absolute value from the detected fourth-order spherical aberration;

a3) if the detected spherical aberration is positive, supplying said excimer laser unit with an overcorrect photoablative pattern that results in an induced fourth-order positive spherical aberration after treatment, the overcorrect photoablative pattern being obtained by obtaining a photoablative pattern to correct a fourth-order spherical aberration that is opposite in sign and increased numerically in absolute value from the detected fourth-order spherical aberration; and

a4) controlling said excimer laser unit to implement the overcorrect photoablative pattern on said cornea.

2. The control method as claimed in claim 1 ;

wherein said step a) also comprises the step of:

b) controlling said excimer laser unit to perform specific photoablative treatment related to the visual defect of the eye associated with the presbyopia.

3. The control method as claimed in claim 2 ;

wherein said step b) comprises the steps of:

c) if the visual defect of the eye is hypermetropia, controlling said excimer laser unit to perform the following operations:

c1) ablation of a circular corona of maximum 6 mm inside diameter, maximum 9 mm outside diameter, and of such a depth as to compensate the spherical defect;

c2) ablation with a customized ablative pattern to eliminate higher than second-order defects, with reference to aberrometric data acquired prior to the operation in the preceding point; and

c3) if the above operations fail to achieve a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0, ablation with a customized ablative pattern to obtain even greater spherical aberration;

d) if the visual defect of the eye is hypermetropia and positive astigmatism or hypermetropia and negative astigmatism, controlling said excimer laser unit to perform the following operations:

d1) cylindrical ablation, with the excimer laser unit set solely to the cylindrical defect, to bring the cylindrical defect close to zero;

d2) ablation of a circular corona of maximum 6 mm inside diameter, maximum 9 mm outside diameter, and of such a depth as to compensate the spherical defect;

d3) ablation with a customized ablative pattern to eliminate higher than second-order defects, with reference to aberrometric data acquired prior to the operation in the preceding point; and

d4) if the above operations fail to achieve a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0, ablation with a customized ablative pattern to obtain even greater spherical aberration;

e) if the visual defect of the eye is myopia, controlling said excimer laser unit to perform the following operations:

e1) ablation to such a depth as to compensate the spherical defect; and

e2) ablation with a customized ablative pattern to induce positive spherical aberration with a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0;

f) if the visual defect of the eye is myopia and positive astigmatism or myopia and negative astigmatism, controlling said excimer laser unit to perform the following operations:

f1) cylindrical ablation, with the excimer laser unit set solely to the cylindrical defect, to bring the cylindrical defect close to zero;

f2) ablation to such a depth as to compensate the spherical defect; and

f3) ablation with a customized ablative pattern to induce positive spherical aberration with a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0;

g) if the visual defect of the eye is emmetropia, controlling said excimer laser unit to perform:

g1) operations d2), d3) and d4), if the visual defect improves using a positive lens; and

g2) operations e1) and e2), if the visual defect improves using a negative lens;

h) if the visual defect of the eye is positive astigmatism or negative astigmatism, controlling said excimer laser unit to perform:

h1) operation d1) to achieve emmetropia;

h2) operations d2), d3) and d4), if the visual defect improves using a positive lens; and

h3) operations e1) and e2), if the visual defect improves using a negative lens.

4. The control method as claimed in claim 1 , also comprising the step of:

i) controlling said excimer laser unit to form on the cornea a photoablative pattern which also corrects higher-order aberrations.

5. A controller for an excimer laser unit which performs cornea ablation to reduce presbyopia, the controller comprising:

a) first control means that controls said excimer laser unit to form on the cornea a photoablative pattern inducing a fourth-order ocular aberration;

wherein said induced fourth-order aberration is a spherical aberration; and

wherein said first control means comprise:

a1) aberrometric measuring means that acquires and interprets an aberrometric map of the eye indicating the visual defects of the eye, said visual defects comprising second-order visual defects including hypermetropia, astigmatism, and myopia, and higher-order visual defects including spherical aberration;

a2) first photoablative pattern generating means which are activated, if the detected spherical aberration is negative, to generate an overcorrect photoablative pattern that results in an induced fourth-order positive spherical aberration after treatment, the overcorrect photoablative pattern being generated by generating a photoablative pattern to correct a fourth-order spherical aberration that is numerically increased in absolute value from the fourth-order spherical aberration detected by said aberrometric measuring means;

a3) second photoablative pattern generating means which are activated, if the detected spherical aberration is positive, to generate an overcorrect photoablative pattern that results in an induced fourth-order positive spherical aberration after treatment, the overcorrect photoablative pattern being generated by generating a photoablative pattern to correct a fourth-order spherical aberration that is opposite in sign and numerically increased in absolute value from the fourth-order spherical aberration detected by said aberrometric measuring means;

a4) supply means that supplies the overcorrect photoablative pattern so generated to said excimer laser unit for implementation on said cornea.

6. The controller as claimed in claim 5 ;

wherein said first control means:

c) if the visual defect of the eye is hypermetropia, control said excimer laser unit to perform the following operations:

c1) ablation of a circular corona with a maximum 6 mm inside diameter and a maximum 9 mm outside diameter, and of such a depth as to compensate the spherical defect;

c2) ablation with a customized ablative pattern to eliminate higher than second-order defects, with reference to aberrometric data acquired prior to the operation in the preceding point; and

c3) if the above operations fail to achieve a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0, ablation with a customized ablative pattern to obtain even greater spherical aberration;

d) if the visual defect of the eye is hypermetropia and positive astigmatism or hypermetropia and negative astigmatism, control said excimer laser unit to perform the following operations:

d1) cylindrical ablation, with the excimer laser unit set solely to the cylindrical defect, to bring the cylindrical defect close to zero;

d2) ablation of a circular corona of maximum 6 mm inside diameter, maximum 9 mm outside diameter, and of such a depth as to compensate the spherical defect;

d3) ablation with a customized ablative pattern to eliminate higher than second-order defects, with reference to aberrometric data acquired prior to the operation in the preceding point; and

d4) if the above operations fail to achieve a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0, ablation with a customized ablative pattern to obtain even greater spherical aberration;

e) if the visual defect of the eye is myopia, control said excimer laser unit to perform the following operations:

e1) ablation to such a depth as to compensate the spherical defect; and

e2) ablation with a customized ablative pattern to induce positive spherical aberration with a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0;

f) if the visual defect of the eye is myopia and positive astigmatism or myopia and negative astigmatism, control said excimer laser unit to perform the following operations:

f1) cylindrical ablation, with the excimer laser unit set solely to the cylindrical defect, to bring the cylindrical defect close to zero;

f2) ablation to such a depth as to compensate the spherical defect; and

f3) ablation with a customized ablative pattern to induce positive spherical aberration with a coefficient of Zernike's polynomial Z 4 0 ranging between 0.1 and 1.0;

g) if the visual defect of the eye is emmetropia, control said excimer laser unit to perform:

g1) operations d2), d3) and d4), if the visual defect improves using a positive lens; and

g2) operations e1) and e2), if the visual defect improves using a negative lens;

h) if the visual defect of the eye is positive astigmatism or negative astigmatism, control said excimer laser unit to perform:

h1) operation d1) to achieve emmetropia;

h2) operations d2), d3) and d4), if the visual defect improves using a positive lens; and

h3) operations e1) and e2), if the visual defect improves using a negative lens.

7. The controller as claimed in claim 5 ;

wherein the first control means also controls said excimer laser unit to form on the cornea a photoablative pattern which also corrects higher-order aberrations.

8. A method of reducing presbyopia, comprising:

acquiring and interpreting an aberrometric map of the eye indicating at least one visual defect of the eye, the order of said visual defect being forth-order or less; and

controlling an excimer laser unit to form on the cornea a photoablative pattern inducing a fourth-order spherical ocular aberration, resulting in a forth-order spherical ocular aberration after treatment.