Ch Dohlman

Boston keratoprosthesis with titanium back plate

Purpose Following implantation of a Boston Keratoprosthesis (BKPro), formation of a retroprosthetic membrane (RPM) is an indication of postoperative intraocular inflammation. The purpose of this retroactive study has been to compare BKPro back plates made of titanium with the standard PMMA back plates. Any difference in RPM formation would guide our future choice of material for the device. Methods The design was a retroactive analysis looking at the surgical outcomes after 6 months in patients who had BKPro implants. Pediatric cases were excluded. The indications for having a KPro implant were broadly divided into three categories: autoimmune (n=12), chemical burns (n=11), and others (non-autoimmune) (n=55). Three types of back plates were studied: 1) threaded (screw-on) PMMA (n=39), 2) non-threaded (snap-on) PMMA (n=16) and 3) non-threaded titanium back plates (n=23). Main outcome measured was incidence of RPM formation at 6 months after surgery that warranted removal by either YAG laser membranotomy or surgery. Results The percentage of patients who developed RPM was greatest in the threaded PMMA group (46%), followed by the non-threaded PMMA (31%), although this difference did not achieve statistical significance (p=0.5). The non-threaded titanium group showed the least RPM formation (13%), which was significantly less than both the threaded PMMA (p=0.002) and the threadless PMMA (p=0.043) groups. Conclusion Titanium KPro back plates induce less RPM than PMMA back plates, threaded or non-threaded. It seems that the titanium plates in this setting are more tissue friendly and cause less inflammation than PMMA.