Confocal Microscopy and Optical Coherence Tomography to Evaluate Explanted Titanium Back Plate Type Keratoprosthesis

Abstract

Purpose : A recent development in keratoprothesis (KPro) technology is the titanium back plate. The goal of the current study was to evaluate titanium back plate KPros explanted due to sterile melts using confocal microscopy and optical coherence tomography (OCT).

Methods : Three titanium back plate KPros were collected from patients undergoing explantation and exchange at Bascom Palmer Eye Institute, Miami, FL, USA. Prior to explantation, patients underwent OCT imaging of the anterior segment to visualize the integrity of the donor cornea and KPro configuration. In the operating room, the KPro samples were immediately placed in a container with balanced salt solution after removal. Samples underwent full microbiological workup (culture, stain and PCR) and histopathological analysis. The entire anterior and posterior surfaces of each KPro were examined with fluorescent confocal microscopy (Leica 5PS) using a live/dead stain to visualize microbial activity, biofilm deposition, and cellular adhesion.

Results : Microbiology samples from all three cases were culture negative. In one case, the histopathological analysis revealed fibrovascular tissue. Confocal microscopy revealed extensive retroprosthetic membranes on the interior surface of all KPros, especially in the area of the click-on gap. Biofilm deposition was present on all three KPros. In one case, biofilm deposition was present between the external optic surface and donor cornea, corresponding to an area of corneal melting imaged by OCT imaging (Figure 1).

Conclusions : Multidisciplinary imaging techniques can help the clinician evaluate KPro patients and possibly predict complications, as well as provide insight onto the mechanism of failure when complications do occur. Titanium is biocompatible, and is used in a variety of biomedical implants mostly because of its surface features; however the roughness of the titanium inside the eye provides a site where microorganisms and retroprosthetic membranes can adhere. For KPro implants, using a well-polished biocompatible material, such as used in intraocular lenses, may be better.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Confocal microscopy images of (left) external and (right) internal surfaces of titanium keratoprosthesis after explantation from patient secondary to sterile melt. (Bottom) OCT image of keratoprosthesis prior to explantation showing separation between donor cornea and the stem of the optical cylinder.