Eye bank versus surgeon prepared DMEK tissues: influence on adhesion and re-bubbling rate.

AIM: To investigate the difference in adhesion and rebubbling rate between eye bank and surgeon prepared Descemet membrane endothelial keratoplasty (DMEK) tissues. METHODS: Laboratory and clinical retrospective comparative interventional case series. Research corneal tissues were obtained for laboratory investigation. The clinical study involved patients with endothelial dysfunction who underwent DMEK surgery and tamponade with air. Tissues were stripped using a standard DMEK stripping technique (SCUBA) and shipped as prestripped or loaded in a 2.2 intra-ocular lens cartridge with endothelium facing inwards (preloaded) before transporting from the eye bank to the surgeon. For surgeon prepared tissues, all the grafts were stripped in the theatre and transplanted or stripped in the laboratory and tested immediately. Adhesion force and elastic modulus were measured in the centre and mid-periphery in a laboratory ex vivo investigation using atomic force microscopy, while rebubbling rates were recorded in the clinical study. RESULTS: There was no difference in endothelial cell viability between surgeon or eye bank prepared tissue. Surgeon-stripped DMEK grafts in the laboratory investigation showed significantly higher elastic modulus and adhesion force compared to prestripped and preloaded tissues (p<0.0001). In the clinical data, rebubbling rates of 48%, 40% and 15% were observed in preloaded, prestripped and surgeon-stripped DMEK grafts, respectively. Rebubbling rates were significantly associated with combined cataract surgery (p=0.009) and with time from harvesting the graft to the surgery (p=0.02). CONCLUSIONS: Decreased adhesion forces and elastic modulus in eye bank prepared tissues may contribute to increased rebubbling rates.

In vitro establishment, validation and characterisation of conjunctival epithelium outgrowth using tissue fragments and amniotic membrane.

BACKGROUND/AIMS: To set up the in vitro conditions for renewal of the conjunctival epithelium using healthy fragments of conjunctival tissue glued over an amniotic membrane. METHODS: We evaluated the capability of conjunctival tissue fragments to generate conjunctival cell outgrowth after seeding them onto amniotic membrane and culture plates; we then assessed conjunctival molecular marker expression by immunofluorescence. We also evaluated the efficiency of glueing the fragments over the amniotic membrane to determine the best setting and the feasibility of shipping preloaded amniotic membranes. RESULTS: Epithelial outgrowth was detected in 65%-80% of conjunctival fragments starting 48-72 hours after glueing, without major differences between type of membrane preparation and fragment size. Within 6-13 days, a full epithelium covered the surface of the amniotic membrane. Specific marker expression (conjunctival epithelium, Muc1, K19, K13; stemness, p63; tight junctions, ZO-1) was detected. Results of the shipping test showed that only 31% of the fragments were still glued over the epithelial side of the membrane within 24 hours compared to more than 90% of fragments stayed attached in the remaining conditions. CONCLUSION: The in vitro regeneration of conjunctival epithelium following outgrowth from conjunctival tissue fragments glued over an amniotic membrane may offer a viable strategy to renew the epithelium in vivo once applied over the ocular surface at the recipient site.