Possibilities of cornea storage in cornea banks

1.1. At the earliest times when the whole eye was stored in humidity chamber at +4 °C was called the short term method. During the process the endothelial cells that are responsible for the transparency started falling into decay and after the next 24 hours it became even intense. So these kinds of corneas should have been implanted within 48 hours.
1.2. According to the latter procedure the cornea is separately stored just as in tissue culture. In this the same +4 °C storage condition however now enables cornea to be stored alive for four days.

2. In the mid-term or ’cold’ storage method has been applied since 1984 and enables cornea to be stored for 14 days at +4 °C. Until present several mid-term storage solutions spread in the United States and Europe as well.

3. The long term or ’warm’ storage method was worked out at the University of Minnesota in 1972. This procedure enables cornea to be stored for 30 days at 31 °C. The nutrition solution had to be replaced every two-three days in 5% CO2 atmosphere. The improved technique did the replacement only weekly in 1979.
Today in organ culture preservation corneas are incubated in tissue culture medium supplemented with fetal bovine serum, antibiotics, and fungicide. Before transplantation by placing the corneas to a culture medium supplemented with Dextran, the swelling of the cornea due to the absence of dehydrating agents in the medium is reversed shortly. The integrity of the endothelium is better maintained during organ culture than cold storage.
The banks belonging to the European Eye Bank Association received almost 40,000 corneas every year and 80% of them are stored in organ culture medium at 31 °C.

4. The other method for long distance cornea storage is refrigeration. The first successful transplantation from refrigerated cornea was made in 1954, but the quite expensive and difficult method had only 70% efficiency. The endothelial cells however survive refrigeration this method has not spread in practice.