Ophthalmological patient interface device

An ophthalmological patient interface device for application onto a cornea of an eye during treatment of the eye, the ophthalmological patient interface device comprising:

• a coupling part configured to attach mechanically the ophthalmological patient interface device to an optical projection system of an ophthalmological apparatus,
• a firm, ring-shaped, and transparent contact part configured to contact a ring-shaped first surface area of the cornea, when the ophthalmological patient interface device is applied on the cornea for the treatment of the eye, while leaving uncovered by the contact part an inner second surface area of the cornea, surrounded by the first surface area of the cornea, and to let pass a laser beam from the optical projection system through the contact part into eye tissue covered by the ring-shaped first surface area of the cornea, when the ophthalmological patient interface device is coupled to the optical projection system for the treatment of the eye, and
• a wall extending from the contact part to the coupling part and encompassing a hollow space for filling liquid into the hollow space when the ophthalmological patient interface device is applied on the cornea for the treatment of the eye,
• the contact part having a reference surface for contacting the cornea and a receiving surface which is averted from the reference surface,
• at least part of the receiving surface bordering onto the hollow space such that, when the ophthalmological patient interface device is coupled to the optical projection system, when said laser beam is directed into said eye tissue of the ring-shaped first surface area of the cornea, said laser beam travels from the optical projection system through the liquid filled into the hollow space, through the receiving surface and through the reference surface into the eye tissue, and when said laser beam is directed into eye tissue covered by the inner second surface area of the cornea, said laser beam travels from the optical projection system through the liquid filled into the hollow space into the eye tissue without passing through the contact part.