This has been used orally for penetrating keratoplasty. A recent study from Japan has shown it’s effectiveness as a 0.02% ointment (Miyazaki et al. 2008 Ophthalmology 2008). Tacrolimus is 20 times more potent than cylcosporin and blocks NFAT-dependent T-cell activation and NFAT-dependent B cell and mast cell functions. Topical tacrolimus ointment has been approved for skin complaints such as atopic dermatitis and this has been used for eyelid diseases, but an ointment form for use in the conjunctival fornix remains to be marketed commercially. In the Japanese study, the ointment was made by diluting the more concentrated 0.1% ointment used for the skin with ofloxacin ointment, the base for which is purified lanolin. It was effective in treating peripheral ulcerative keratitis secondary to scleritis and atopic keratoconjunctivitis. In the above study, few side effects were noted, but the ointment did burn when applied to the eye. Tacrolimus eyedrops have previously been associated with recurrent herpes simplex keratitis.