The examination of the optically transparent cornea requires a special lighting technique via an illuminated slit projected onto the eye. 
The known state-of-the-art treatment devices, specifically refractive lasers for refractive surgeries on the eye, do not include these slit projection devices.  Rather, it is common practice to examine the patient using an examination system at a separate location after completing the surgery.  The disadvantage of this procedure is that the patient has to get up and that possible problems cannot be alleviated immediately on site with the surgical microscope. 
Another known solution, as is being practiced on the refractive laser device MEL80 by Carl Zeiss Meditec AG, provides for the adaptation of a slit illumination projector on the treatment device which can be transported into several positions necessary for the procedure via a guide mechanism.  The main disadvantage here is the patient's and operator's freedom of movement being limited by the guide mechanism.  Furthermore, the operating field light must be switched off separately while the slit lamp illumination is being used. 
Further disadvantages lie with the halogen lamps used as a state-of-the-art light source for the slit illumination—their short lifespan and high heat-radiation.