96 |
|
E. Pels and G. Pollock |
|
|
|
Table 6.2 Storage procedures for the corneoscleral button |
|
|
Factors to consider |
Hypothermic |
Organ culture |
Technique |
Simple and fast |
More complex |
|
Minimal handling |
|
Storage time |
Up to 10 days |
Up to 4–7 weeks |
Tissue available for |
Yes |
No |
direct use |
|
|
Maintenance |
Yes |
No |
hydration |
|
Reversal swelling necessary |
Epithelial and endothelial |
No |
Yes |
wound healing |
More strict concerning |
More tolerant for conditions |
|
donor supply |
affecting endothelial viability |
Evaluation tissue |
Non-invasive |
Invasive |
technique |
Specular microscope |
Light microscopy |
|
(invasive light microscopy) |
|
Evaluation endothelium |
Small central area |
Entire surface |
Risk primary graft failure |
Overall reported mean 2% |
0–0.3% |
|
Currently estimated 1% |
|
|
Greater when storage time > 7 days |
|
Graft survival |
|
At least comparable |
Microbiological tests |
Not required |
Mandatory |
|
|
Quarantine period |
|
|
More tolerant for |
|
|
septicaemic risk donor |
Risk of post-operative |
0.1–2% |
0–0.1% |
endophthalmitis |
|
|
Storage solutions |
Commercial available |
Commercial available/ |
|
|
in-house manufacture |
normothermically at 30–37°C, the “organ culture” method introduced in 1976 by Doughman. These techniques require good asepsis and careful application, and increasingly, eye banks are implementing quality assurance programs for good tissue banking practice to ensure the quality and validity of processes. The different storage procedures for the corneoscleral button are summarised in Table 6.2. Although some success has been reported with corneas frozen in liquid nitrogen, it is not a generally accepted storage method for corneas.
Moist Chamber Storage of the Donor Eye
Technical Aspects
The enucleated eye is placed in a sealed chamber together with gauze, moistened with saline or an antibiotic solution and stored at 2–6°C. Immersion in the saline solution must be prevented to avoid the cornea taking up extraneous fluid that would result in epithelial and stromal oedema.