Atomic force microscopy shows reduced elasticity of prolonged cold-stored DMEK graft
Longer graft storage time in cold media significantly reduced the elasticity of a Descemet’s membrane endothelial keratoplasty graft, with potential effects on unfolding within the anterior chamber as well as postoperative detachment rate.
“Unfolding difficulties with tight grafts are one of the most common challenges of DMEK,” Natalya Shilova, MD, said at the virtual European Society of Cataract and Refractive Surgeons meeting.
In the study Shilova performed with her group, atomic force microscopy (AFM) was used to measure the effect of graft storage time on the elastic properties of DMEK grafts. AFM, she said, is a technology that measures the elastic properties of membranes by scanning them with the microtip of a cantilever, which deflects in correlation with the membrane elastic modulus.
The grafts were prepared from 20 human corneas of 10 donors unsuitable for transplantation. Ten were stored for 1 day in Optisol-GS (Chiron Ophthalmics) at 4°C (group A). The paired corneas of same donors were stored in the same medium at the same temperature for 1 week (group B). The mean age of donors was 66 years, mean death to tissue harvest time was 15 hours, and endothelial cell count (ECC) did not differ between the groups.
“We measured elasticity with the Integra atomic force microscope (NT-MDT) and found a larger indentation depth in group A as compared with group B. Force-distance curve analysis showed increase in the Young modulus of elasticity in group B in comparison with group A, with a mean value of 10.8 vs. 6.3,” Shilova said.
A longer storage time reduced the elasticity of the graft, while no correlation was found with age, ECC or procurement interval.
“Clinically, this could potentially influence the unfolding of the graft during surgery and have an effect on the posterior detachment rate,” Shilova said. “In our clinical experience, we found that grafts that we were able to use after 2 or 3 days were easier to unfold, and no detachment occurred, but this has to be verified by further comparative studies.”
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Shilova N, et al. The effect of DMEK graft storage time on its elasticity. Presented at: European Society of Cataract and Refractive Surgeons meeting; Oct. 2-4, 2020 (virtual meeting).
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