The aim of the present paper is to describe the morphological changes that
occur in human corneal endothelium as an immediate consequence of corneal c
ryopreservation. Therefore, 16 human donor corneas were cryopreserved with
an original procedure at a 1 degrees C/min cooling rate in a freezing solut
ion cryoprotected with 7% dimethylsulphoxide until a final temperature of -
100 degrees C was reached. After storage of the corneas in liquid nitro gen
for periods ranging from 1 to 96 days (mean: 34.31 days), the corneas were
thawed in a water bath at +37 degrees C. Eight additional control corneas
were processed without cryopreservation. Morphological assessment of the en
dothelial layer was performed by scanning electron microscopy and trypan bl
ue and alizarin red S vital staining. Results showed cryoinduced damage at
variable degrees in all cryopreserved corneas. They were classified into th
ree groups according to the intensity and extension of the cryoinduced dama
ge: group I (n = 10): corneas with minor endothelial alterations consisting
in the presence of microholes in the posterior cell membrane; group II (n
= 1): corneas with generalized disruption of endothelial intercellular junc
tions and intact cell membranes; group III (n = 5): corneas with severe end
othelial damage consisting of massive cell necrosis and complete alteration
of the morphological pattern of the endothelium. All control corneas had i
ntact endothelial layers. Cryoinduced damage cannot be completely avoided w
ith the cryopreservation protocol tested. The high interindividual variabil
ity of the results observed is not related to the storage time of the corne
a in liquid nitrogen.