An apparatus for performing ophthalmic surgery, comprisinga light source configured to generate a light beam；a focusing lens in optical communication with the light source, the focusing lens configured to focus the light beam into a focus light beam；a contact glass element configured to contact an eye to be treated, the contact glass element having a transmission ratio of at least 90% relative to the focused light beam and configured to introduce a wavefront error of at most about λ/2 to the focused light beam when the focused light beam passes through the contact glass element, wherein the focusing lens is configured such that the focus light beam has a region of focus within a cornea of the eye, the region of focused having a diameter of 15µm or less； andoptical means configured to direct the focused light beam having a region of focus with a diameter of 15mm or less repeatedly and successively over a treatment region within the cornea of the eye to form an incision in the cornea, wherein said contact glass element comprises a material having an index of refraction in the range of 1.500 to 1.550 relative to the focused light beam.
