Objective: To investigate the clinical and histopathologic features of the superficial tissue proliferation (STP) following the implantation of MICOF keratoprosthesis, and to analyze the formation and treatment of STP.
Methods: Retrospective study. Eighty-five patients (85 eyes) received MICOF keratoprosthesis surgery from January 2000 through December 2009 in General Hospital of PLA, which included 72 males and 13 females. The mean age of the patients was (45 ± 15) years. Preoperative diagnoses were ocular burn (56 eyes), end-stage of autoimmune dry eye (14 eyes), severe ocular trauma (10 eyes) and repeated graft failure (5 eyes). Postoperatively, STPs of Kpro were observed and treated. The membranes anterior to the optical cylinder were removed and investigated by histological and immunohistochemical methods, and anterior segment specimens from normal eyes were taken as control.
Results: Twenty-two (26%) patients presented STP during the follow-up, and proliferations occurred ranging from 2 to 63 months (median, 7 months). The incident rates of STP were 34% (19/56 eyes) in burned eyes, 14% (2/14 eyes) in end-stage dry eye, 10% (1/10 eyes) in severe mechanical ocular trauma, and none in repeated grafts failure. Difference among four groups did not arrive significance statistically (χ(2) = 5.93, P = 0.11). The epithelial proliferations were observed in 11 patients, which were removed easily. To prevent from recurrence, the height of the cylinder was adjusted. Other 4 patients underwent ultra-high frequency ocular surface plastic operation and 7 patients received membranectomy. Histologically, the superficial proliferative membrane was composed of proliferative epithelium and fibrovascular tissue incorporating inflammatory cells. The immunohistochemical staining demonstrated the expression of PCNA increased in the epithelium, compared with control cornea and conjunctiva. Many vimentin-positive fibroblasts and a few α-SMA-positive myofibroblasts presented in the interstitial tissue, and the numbers of CD45RO-positive T cells, CD11c-positive dendritic cells, and CD68-positive macrophages were increased in proliferative membranes.
Conclusions: The tissue proliferation around optical cylinder results in membrane formation anterior to the Kpro. The excessive inflammation at the prosthesis-corneal junction and the unsuited height of the optical cylinder might have been the main reasons of STP.