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Joel Palko, Yanhui Ma, Maxwell William Dixon, Keyton Clayson, Augustine Hong, Anthony Lubniewski, Jun Liu; Mechanical stability of partial thickness tectonic corneal grafts. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1393. doi: https://doi.org/.
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“Split-thickness grafting,” a process in which corneal endothelium from a donor is transplanted into one patient and the residual anterior stroma into another, has been used to optimize the use of corneal grafts in locations where tissue demand exceeds supply. This study investigates the potential to cryopreserve anterior stromal tissue obtained from a Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) procedure for later utilization by comparing the ex vivo mechanical stability of fresh and cryopreserved partial thickness tectonic corneal grafts.
Pressure controlled inflation testing utilizing a previously validated ultrasound speckle tracking technique (Fig 1) was used to analyze axial (compressive) and lateral (tensile) strains of paired residual anterior stromal grafts following a DSAEK procedure. One graft from each set of corneas (n=4) was frozen in liquid nitrogen and stored at -80°C for 3 months, while its counterpart was tested fresh. Age matched (n=3) full thickness corneal grafts were used as controls. A 4 mm circular graft was sutured into a whole globe with a central 3 mm full thickness corneal perforation. The superior-inferior oriented strains were measured while inflating the globe from an intraocular pressure (IOP) of 5 to 30 mmHg. The IOP at graft failure was then recorded. The mean axial and lateral strains at 30 mmHg and IOP at failure were compared between the fresh and frozen anterior stroma grafts using a paired t-test. These variables were compared amongst the three groups using a general linear model with corneal thickness as a covariate.
No statistically significant differences were found between the axial and lateral strains at 30 mmHg (p=0.83 & p=0.56) or IOP at failure (p=0.73) in fresh (Ax 0.088±0.039, Lat 0.014±0.007, IOP 194±70 mmHg) and frozen (Ax 0.081±0.019, Lat 0.010±0.009, IOP 174±93 mmHg) anterior stromal grafts (Fig 2). No statistically significant differences in any of the mean strains or IOP at failure (p=0.55) were found between the anterior stromal grafts and full thickness grafts (Ax 0.080±0.035, Lat 0.014±0.022, IOP 210±110 mmHg).
The pressure-strain relationship and IOP at failure were similar amongst the three groups of grafts, providing evidence that microkeratome dissected fresh and cryopreserved anterior stromal grafts may be suitable as short-term tectonic corneal grafts.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Representative strain map in a partial thickness graft.
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