The invention relates to an apparatus for changing the refractive power of the cornea (1), in particular for correcting hyperopia or presbyopia, exhibiting injection means (13, 15) having at least one hollow needle (15) for injecting at least one optically transparent filling material having a predetermined refractive index into an intrastromal corneal pocket (7), characterized by a controllable injection drive (17) that is coupled at least indirectly to the injection means (13, 15) and is designed for changing an amount, to be injected, of the at least one filling material; a device for optical coherence tomography (OCT) (19) that is designed for monitoring the area of the corneal pocket (7) by means of measurement of depth profiles of the cornea (1) on a repeatedly cycled-through scan pattern; and a computing unit (21) that is designed and/or configured to determine from the measurement data of the OCT device (19) at least the radius of curvature of the front (3) of the cornea (1) keeping pace temporally with the repetitions of the scan pattern cycle during the injection, wherein the computing unit (21) is designed and/or configured to control the injection drive (17) for changing the injected amount of the at least one filling material, and namely on the basis of the radius of curvature of the front (3) of the cornea (1) and/or such until a predetermined target criterion is fulfilled.