CHARACTERISTICS OF INFECTIOUS AND NON-INFECTIOUS VITRITIS IN BOSTON KERATOPROSTHESIS TYPE I: 18 YEARS OF EXPERIENCE AND OUTCOMES FROM A SPANISH REFERENCE CENTER. Abbreviated tittle: VITRITIS IN BOSTON KERATOPROSTHESIS.

PURPOSE: To assess the incidence, characteristics, management and outcomes after infectious and non-infectious vitritis in patients with Boston type 1 Keratoprosthesis (BKPro1). METHODS: A retrospective chart review was conducted of all patients who developed vitritis following BKPro1 surgery at Cruces University Hospital between June 2006 and June 2024. The main outcomes analyzed were: type of vitritis, treatment and management, etiopathogenesis, and pre- and post-vitritis visual acuity (BCVA). RESULTS: Over 18 years, 79 eyes underwent BKPro1 surgery. The mean follow-up was 8.25 ± 5.34 years. A total of 18 eyes suffered from vitritis, corresponding to an incidence of 22.7%. Out of 18 vitritis, 38.9% were diagnosed as reactive vitritis, 5.5% as idiopathic vitritis, and 55.6% as endophthalmitis. The median time to develop vitritis was 6.5 months [2 - 25.75]. PPV was performed in 100% of cases. Most identified pathogens were Gram-positive, mainly Staphylococcus epidermidis. In the endophthalmitis group, 30% of patients achieved a final BCVA similar to their pre-infectious baseline. Patients who underwent surgery on the same day as diagnosis were able to maintain the implant and BCVA. Failure to improve BCVA in the reactive vitritis group was mainly due to postoperative complications. In the idiopathic vitritis case, visual recovery occurred at 3.85 weeks after treatment. CONCLUSION: These three vitritis patterns may represent variations of the same underlying process. Given the low morbidity of modern vitrectomy, early surgical intervention should be considered in cases of diagnostic uncertainty, as this is a vision-threatening condition that requires prompt recognition and management.