System comprising a planning device for determining control data for a treatment apparatus for correcting a refractive error of an eye of a patient by surgery and a measuring device connected directly to the planning device, wherein - the measuring device comprises an OCT and generates measurement data relating to parameters of the eye and transmits these to the planning device, - the planning device generates the control data for a treatment apparatus comprising a laser device which separates corneal tissue by radiating in pulsed laser radiation, wherein the laser radiation is focused on target points located in a pattern in the cornea and the planning device generates a control data record for driving the laser device, said control data record setting a pattern of the target points, characterized in that - by using the OCT, the measuring device generates refractive error data about the refractive error of the eye to be corrected and transmits said data to the planning device, wherein the refractive error comprises hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism where there is hyperopia in one direction and myopia in a direction at right angles thereto), aspherical errors and/or higher order aberrations, - the planning device determines an interface (19, 20) from the measurement data and refractive error data and - the planning device generates the control data record for driving the laser device for this interface (19, 20), wherein the control data record sets a three-dimensional pattern of the target points in the cornea, said target points lying at the interface (19, 20) and being arranged such that the interface (19, 20) is embodied as a cut surface after radiating in the pulsed laser radiation in accordance with the control data record. - the measuring device comprises an OCT and generates measurement data relating to parameters of the eye and transmits these to the planning device, - the planning device generates the control data for a treatment apparatus comprising a laser device which separates corneal tissue by radiating in pulsed laser radiation, wherein the laser radiation is focused on target points located in a pattern in the cornea and the planning device generates a control data record for driving the laser device, said control data record setting a pattern of the target points, characterized in that - by using the OCT, the measuring device generates refractive error data about the refractive error of the eye to be corrected and transmits said data to the planning device, wherein the refractive error comprises hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism where there is hyperopia in one direction and myopia in a direction at right angles thereto), aspherical errors and/or higher order aberrations, - the planning device determines an interface (19, 20) from the measurement data and refractive error data and - the planning device generates the control data record for driving the laser device for this interface (19, 20), wherein the control data record sets a three-dimensional pattern of the target points in the cornea, said target points lying at the interface (19, 20) and being arranged such that the interface (19, 20) is embodied as a cut surface after radiating in the pulsed laser radiation in accordance with the control data record.