An apparatus for the treatment and/or prevention of corneal diseases includes an applicator head. The applicator head includes a radiation source capable of exciting a non-toxic chromophore. A control is operable to activate the radiation source to radiate, wherein at least one of the following two conditions is met: the applicator head includes a sensor capable of measuring a signal dependent on a position of the applicator head relative to the cornea； or, the applicator head is configured to be in physical contact with the cornea. The control is operable to activate the radiation source to radiate depending on a signal measured by the sensor or to activate the radiation source when the applicator head touches the cornea, respectively.
