In-Vivo Confocal Microscopy In Porcine Collagen Implants In Advanced Keratoconus

Collagen crosslinking (CXL) was originally described to stabilize progressive keratoconus (KC) in corneas with a stromal thickness of more than 400μ to avoid endothelial damage. The last decade witnessed the development of tissue addition techniques in cases of advanced ectasia not suitable for CXL. Xenogeneic corneal transplants are recently being explored to overcome the issue of global shortage of tissues. Porcine corneas have been shown to be physiologically similar to human cornea and hence, a preferred choice for xenotransplantation.Xenia^TM lenticules are decellularized stromal lenticules derived from porcine corneas.This study reports the clinical and confocal microscopic outcomes of Xenia implants in cases of advanced KC at 1 year.

This was a prospective interventional study on KC eyes intolerant to contact lenses,pachymetry<400μ and not suitable for CXL. Eyes with corneal scar, corneal infections, previous corneal surgeries, pregnant females were excluded. Femtosecond laser assisted stromal pockets were created & porcine collagen stromal lenticule implanted and centred over corneal apex. Visual acuity, corneal topography (Pentacam) ,in vivo confocal microscopy(IVCM) (HRT III) and corneal OCT were done pre-operatively and at 1-week,1-month,3-months,6-months,1-year. Dendritic cell density (DCD) and stromal keratocyte density were counted using cell counter in the IVCM.

The DCD at the anterior lenticular interface was 6+0.4 cells/mm² preoperatively,14+2.9 cells/mm² at 6 months(p=0.04) and 4+0.17 cells/mm² at 1 year(p=0.9). Similarly, DCD at the posterior interface was 3+0.13 cells/mm² preoperatively,12+0.12 cells/mm² at 6 months(p=0.01) and 4+0.4 cells/mm² at 1 year(p=0.72). The anterior stromal keratocyte density at 6 months was 724+107 cells/mm² and at 1 year was 748+103 cells/mm² which was not significantly different from the preoperative values (p=1.2 & 0.87 respectively). A similar trend was noticed with the posterior stromal keratocytes as well. At 1 year, the lenticule remained acellular with no keratocyte population within the lenticule and there was absence of corneal nerves through the lenticule.

There was significant improvement in the visual acuity and corneal topoography at 1 year follow-up for 8 patients. Two patients required explantation of Xenia due to stromal melt. The inflammation at the anterior and posterior lenticule-stroma interface lasted for 6 months as evidenced by the DCD, and was not significant at 1 year. There was no keratocyte population or corneal innervation within the lenticule at 1 year.