Purpose:
A quantitative study is presented on the deswelling process of edematous corneas from eye bank in Dextran500:HBSS solution. The characteristic time constant of the deswelling process and the resulting residual thickness are studied as a function of the Dextran concentration. Structural effects are revealed by histology and scanning electron microscopy.
Methods:
Hank’s balanced salt solutions (HBSS) are prepared with various Dextran500 concentrations (4, 5, 7, 10, 15% wt.). N = 50 human corneas provided by the French eye bank and stored in organoculture were immerged in specific solution. The thickness was measured in regular time intervals with ultrasound pachymetry. When the final thickness was established, the corneas were examined using light and transmission electron microscopy (TEM).
Results:
Numerical analysis shows that at low Dextran500 concentrations (2 - 3 % wt.), the resulting corneal thickness and the characteristic time of deturgescence remain hazardous, while at high density (7 - 15 % wt.) the process is highly predictable. Histological and ultrastructural analysis confirms the influence of the deswelling process on the ultrastruture of the corneas, and eventually reveals a complete dehydratation for higher concentrations. TEM analysis reveals the disorder of collagen fibrils for thickness above and below the physiological thickness (~ 530 µm), while fibrillar order is established at this specific thickness.
Conclusions:
From the presented results it is possible to predict with accuracy the final corneal thickness and the necessary immersion time in a solution with a specific Dextran500 concentration. While a judicious choice of dextran concentration and deturgescence time permits to reproduce the natural corneas hydration and thickness. However, at concentrations too low the efficiency of the process is low and not predictable and at too high concentrations side effects such as fibrillar disorder occur.
Keywords: cornea: basic science • cornea: storage • refractive surgery: corneal topography