Effects of immersion solutions on corneal tissue strip hydration and thermal shrinkage

摘要

Purpose: To assess the effects of immersion solutions with different Dextran concentrations on the hydration of cornea tissue strips at normal body temperature. Methods: A 20% Dextran-BSS solution was injected via a self sealing limbal-transcorneal tunnel incision using a 30ga needle into the anterior chamber of human donor eyes until the globe was hard. The eyes were then immersed cornea down overnight in the same solution. Corneal thickness was measured by ultrasound pachymetry after the eyes were re-inflated and at regular intervals to assess dehydration. When the central cornea thickness reached 400-500μm corneal buttons were removed using a 10mm trephine. The buttons were then cut into 6×6mm strips using a custom-made jig and immediately immersed in solutions of Dextran (15 to 20% in increments of 2.5%) at 35°C. The edge thickness of the immersed strip was measured every 5 min for one hour using an optical comparator (Topcon, Japan) modified for tissue shadowphotogrammetry. Results: For five Florida Lions Eye Bank donated eyes after one hour in the Dextran solution the mean final measured thickness of corneas in 20%, 17.5% and 15% Dextran-BSS solutions were 570 (5) μm, 680 (0) μm, and 1080 (5) μm respectively. These measured thicknesses changes correspond to an average swelling of 1.2, 1.4 and 2.2 times the initial thickness of each cornea strip in the 20%, 17.5% and 15% Dextran-BSS solutions respectively. Conclusion: This study demonstrates hydration has a significant effect on the thermal stability and shrinkage dynamics of the cornea. A 25% Dextran solution was found to keep corneal tissue strip thickness at normal values.