SD-OCT Complements Histology in Evaluation of Potential Bruch’s Membrane Prosthetics

Abstract

Purpose: : To improve the evaluation of biostable Bruch’s membrane prosthesic materials, and to compare information obtained with OCT follow up relative to resin embedded histo-morphology.

Methods: : Acellular artificial Bruch’s membrane prostheses were either an etched pore polyester membrane (PET/ Corning, Inc.), or a surface-modified expanded polytetrafluoroethylene membrane (ePTFE/ Millipore, Inc.). Bleb retinal detachments were made in Chinchilla bastard rabbits, and an oval shaped implant was inserted subretinally. The rabbits were followed postoperatively at 3, 7, and 14 days with spectral domain (SD) OCT (Spectralis®/ Heidelberg Engineering, Inc.) and with IR& RF fundus photography. Some cases were also imaged with time domain (TD) OCT (C. Zeiss-Meditech, Inc.). To compare histomorphologic artifacts, 4 fixation procedures were evaluated: immersion fixation alone, or coupled with prior perfusion fixation with 4% formaldehyde or 2% glutaraldehyde (GA). Eyes were enucleated either fresh, or after carotid artery perfusion with the fixative. Animals were processed for histology at 3 or 14 days post OP, and full thickness tissue samples embedded in Epon 812 resin and sections cut at 1-2 µm.

Results: : Successful surgeries were followed up by OCT and histology. 2% GA perfusion coupled with immersion fixation yielded superior histomorphology with strong neuroretinal adhesion, as compared to other evaluated methods. SD-OCT and histo sections showed good morphologic correlation. TD-OCT follow up was neither reproducible nor comparable to SD-OCT or histology. No toxicity or adverse reaction was seen around implant sites, when compared to the control eye, for either PET or ePTFE.

Conclusions: : Both solid PET- and fibrillar ePTFE acellular membranes were implantable into the rabbit subretinal space, and well-tolerated in the short term, as demonstrated by SD-OCT and histology. Our findings suggest that the postoperative position of future implants could be preferentially monitored with SD-OCT allowing in vivo "histology", and reducing the number of animals sacrificed.

Keywords: transplantation • Bruch's membrane • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)