Keratoconjunctivitis is a common infectious disease of the eye surface, which is caused by adenovirus. The chronic form is keratitis nummularis. Cyclosporin A is a calcineurin inhibitor which has been used in ophthalmology for approximately 15 years for local therapy of chronic inflammation of the eye surface. Since the 1990s this medication has proven effective for the treatment of keratitis nummularis. The indications for treatment with cyclosporin A eyedrops are given when a reduction in vision due to keratitis nummularis has not shown any improvement within 6 weeks after acute inflammation.