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Maninder S. Bhogal, Emiliano Bilotti, Romesh I. Angunawela, Bruce D. Allan; Quantification of Graft Adhesion In Descemets Stripping Automated Endothelial Keratoplasty. Invest. Ophthalmol. Vis. Sci. 2011;52(14):743.
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Descemets membrane endothelial keratoplasty (DSAEK) is the preferred surgical choice in endothelial dysfunction. Graft dislocation represents a significant early complication. Individual surgeons' variations in the anterior chamber air-fill have up till now been based on anecdotal evidence alone. Our research aims are to quantify the adhesion forces and determine the effect or varying anterior chamber air-fill time and pressure on endothelial graft adhesion.
8 pairs of human corneal tissue were prepared to simulate endothelial grafting. A 350 micron head microkeratome was used to remove the anterior lamellar and the residual endothelial button punched to 8mm. Descemets membrane was removed from the second cornea which was mounted in a customized pressure chamber with a contour matched base. The host cornea was held in place by a low vacuum. A uniform amount of interface fluid was applied, and the endothelial button placed on top. Four variations in time and pressure were applied to each pair of corneas; (A) 60mmHg/8min; (B) 16mmHg/8min; (C) 60mmHg/1min (D) 16mmHg/1min.The force needed to detach the endothelial button from the host was measured using the Instron 5565 tensile test machine, equipped with a 2.5 N load cell, customized grips and Blue Hill software. The endothelial button was attached to the devise by a 6-0 ethilon suture attached to a 2mm aluminum disc placed within the graft host interface. The maximum adhesion force was taken from the force-displacement curve generated.
Adhesive force lies between 0.07 and 1.6 mN/mm2. Mean and standard deviation for total adhesion in the four groups were; (A) 19.2 (22.8); (B) 18.9 (24.1), (C) 15.8 (13.3) and (D) 10.1 (6.3). Intergroup differences failed to reach statistical significance.
For the first time the adhesive forces involved in posterior lamellar surgery have been measured. The descriptive analysis suggests that high pressure and longer time of gas fill produce the highest adhesive force, but further sampling is needed to confirm whether this is statistically significant. These effects are modest in comparison to the variation in adhesive forces witnessed between individual corneas. Further research aimed at identifying the effects of intrinsic factors such as graft thickness and compliance will further our understanding of risk factors important in graft detachment.
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