Bi-radial patient interface

1. A patient interface for an ophthalmic system, comprising:

an attachment portion, configured to attach the patient interface to a distal end of the ophthalmic system;

a contact portion, configured for docking the patient interface to an eye; and

a contact element, coupled to the contact portion, comprising a pre-formed shape that includes, prior to contact with a surface of a cornea of the eye as part of the docking of the patient interface to the eye:

a transparent central portion with a central radius of curvature Rc,

a transparent peripheral portion with a peripheral radius of curvature Rp, wherein Rc is smaller than Rp, and

an edge structure where the transparent central portion and the transparent peripheral portion are joined, the edge structure configured to laterally stretch a central-cornea of the eye during the docking, the edge structure having a central diameter Dc in the range of 6-12 mm.

2. The patient interface of claim 1 , wherein:

Rc is in a range of 6.6 mm-9.1 mm and Rp is in a range of 8.8 mm-10.8 mm.

3. The patient interface of claim 1 , wherein:

Rc is in a range of 7.1 mm-8.1 mm and Rp is in a range of 9.3 mm-10.3 mm.

4. The patient interface of claim 1 , wherein:

the central diameter Dc of the edge is in the range of 8-10 mm; and

the edge structure is configured to stretch a peripheral-cornea area of the eye during docking.

5. The patient interface of claim 1 , the contact portion comprising:

an escape structure, configured to assist an expulsion of air from a contact space between the transparent central portion and the central-cornea.

6. The patient interface of claim 1 , comprising:

a rigid distal lens, configured

to accommodate a proximal surface of the contact element, and

to prevent a more than 5% radial deformation of the contact element upon docking to the eye; and

an affixation structure, configured

to affix the contact element to the contact portion along a perimeter, and

to prevent a more than 5% lateral expansion of the contact element upon docking to the eye.

7. The patient interface of claim 1 , wherein:

the contact element is configured for insertion into the contact portion; and

the contact portion is configured to accept the insertion of the contact element.

8. The patient interface of claim 7 , the contact portion comprising:

a rigid distal lens, having a distal surface with a distal radius of curvature within 5% of a proximal radius of curvature of a proximal surface of the contact element, wherein the distal lens is configured

to form an extended contact with the contact element upon its insertion, and

to prevent a more than 5% radial deformation of the contact element upon the docking to the eye.

9. The patient interface of claim 7 , the contact portion comprising:

an affixation structure, having at least one of

an affixation groove, a support rim, an insertion structure, an interlocking structure, a slide-in structure, a pop-in structure, and a lock-in structure;

wherein the affixation structure is configured

to firmly affix the contact element to the contact portion after the insertion, and

to prevent a more than 5% lateral expansion of the contact element upon the docking to the eye.

10. The patient interface of claim 7 , wherein:

a distal lens, an affixation structure, a material of the contact element and the central radius of curvature Rc are selected such that upon docking the patient interface to the eye, a change of a radius of curvature of the cornea of the eye is greater than a change of the central radius of curvature Rc: ΔR(central-cornea)>ΔRc.

11. The patient interface of claim 1 , wherein:

the contact element comprises a contact material that forms a lubricating film at the surface of the central cornea.

12. The patient interface of the claim 1 , wherein:

a surface of the contact element comprises a hydrophilic material.

13. The patient interface of claim 1 , wherein:

the contact element comprises hydrogel with a water content above 70%.

14. The patient interface of claim 1 , wherein:

the contact element comprises hydrogel with a water content in a range of 50-70%.

15. The patient interface of claim 1 , wherein:

the contact element comprises hydrogel with a water content in a range of 30-50%.

16. The patient interface of claim 1 , wherein:

the contact element has a hydrated index of refraction in the range of 1.32-1.44.

17. The patient interface of claim 1 , the contact portion comprising:

a suction ring, configured

to be coupled to a suction system,

to receive a suction from the suction system, and

to apply the suction of the suction system to a contact space between the patient interface and the eye to dock the patient interface to the eye.

18. The patient interface of claim 1 , wherein

the attachment portion and the contact portion are integrated portions of the patient interface.

19. The patient interface of claim 1 , wherein:

the attachment portion is separate from the contact portion; and

the attachment portion is configured to be coupled to the contact portion after the contact portion has been docked to the eye.