A patient interface for an ophthalmic system can include an attachment module, attachable to the ophthalmic system, and a contact module, configured to accommodate a viscoelastic substance between the patient interface and a procedure eye. The viscoelastic substance can include a fluid, a liquid, a gel, a cream, an artificial tear, a film, an elastic material, or a viscous material. The refractive index of the viscoelastic substance can be within a range of approximately 1.24-1.52 at an operating wavelength of the ophthalmic system. The patient interface can further include input ports, output ports, and a suction system. It can be an integrated design or a multi-piece patient interface. The viscoelastic substance can be provided by injection, on the cornea, at the contact module, or in a space bounded by soft elastic films or membranes, such as in a bag.