Topical citicoline and vitamin B12 versus placebo in the treatment of diabetes-related corneal nerve damage: a randomized double-blind controlled trial

BACKGROUND: To evaluate the effects of topical citicoline and vitamin B12 (Cit-B12: OMK2, Omikron Italia srl, Italy) on corneal innervation of patients with diabetic neuropathy. METHODS: This prospective, randomized, double blind, placebo-controlled study included 30 patients randomised with a 2:1 ratio to Cit-B12 or placebo 3 times daily for 18 months. At baseline and at months 4, 8, 12, 18 patients underwent the Ocular Surface Disease Index questionnaire (OSDI), tear break-up time, evaluation of corneal and conjunctival staining, Schirmer I test, Cochet-Bonnet esthesiometry, and confocal biomicroscopy of corneal sub-basal plexus (SBP). Fiber lenght density (FLD) was calculated using NeuronJ and expressed in mm/mm2. Raw data and differences from baseline were analysed in the two groups. RESULTS: 29/30 patients concluded the study. The two groups had similar FLD at baseline; it progressively improved up to month 18 in both groups (Cit-B12, p < 0.0001; controls, < 0.0001–0.03); improvement at month 18 vs baseline was higher in Cit-B12 than placebo (33% vs 15%, p = 0.04). A progressive amelioration of corneal sensitivity (baseline, 28 ± 18 mm; month 18, 52 ± 10 mm, p < 0.0001), conjunctival staining (P = 0.04) and OSDI questionnaire (P = 0.05) were shown on Cit-B12 group alone. Both treatments were well tolerated and adherence during the study was high. CONCLUSIONS: Cit-B12 ameliorated both morphology and function of corneal nerves in patients with diabetes, thus suggesting a neuroregenerative effect. TRIAL REGISTRATION: Trial registration NCT03906513, retrospectively registered on 08 April 2019.