A medical device for preserving explanted corneas, comprising: a sealed outer main case; a container, for preserving and viewing a cornea, contained in the sealed outer main case; wherein the container in turn comprises: a vessel having a base wall, a lateral wall and an upper opening and which inside it forms a preserving chamber; a supporting unit for a corneoscleral disc positioned in the preserving chamber; and a first lid removably joinable or joined to the vessel for closing the upper opening; wherein the medical device is ready for use and also comprises a first locking ring which is joinable or joined to both the first lid and to the vessel, outside them, and is breakable or deformable; wherein when the first lid is joined to the vessel and the first locking ring is joined both to the first lid and to the vessel: in an intact and non-deformed condition, the first locking ring prevents removal of the first lid from the vessel; and in a broken or deformed condition, the first locking ring allows removal of the first lid from the vessel; and wherein either: - the first lid is joined to the vessel; and the first locking ring is intact and non-deformed, and is joined both to the first lid and to the vessel for preventing them from being separated; and wherein the medical device also comprises a second locking ring joinable to the vessel, also inserted in the outer case and separate from the first lid and from the vessel; or - the first locking ring is separate both from the first lid and from the vessel for, in use, being joined to the vessel and to the lid after a cornea has been inserted in the vessel. a sealed outer main case; a container, for preserving and viewing a cornea, contained in the sealed outer main case; wherein the container in turn comprises: a vessel having a base wall, a lateral wall and an upper opening and which inside it forms a preserving chamber; a supporting unit for a corneoscleral disc positioned in the preserving chamber; and a first lid removably joinable or joined to the vessel for closing the upper opening; wherein the medical device is ready for use and also comprises a first locking ring which is joinable or joined to both the first lid and to the vessel, outside them, and is breakable or deformable; wherein when the first lid is joined to the vessel and the first locking ring is joined both to the first lid and to the vessel: in an intact and non-deformed condition, the first locking ring prevents removal of the first lid from the vessel; and in a broken or deformed condition, the first locking ring allows removal of the first lid from the vessel; and wherein either: - the first lid is joined to the vessel; and the first locking ring is intact and non-deformed, and is joined both to the first lid and to the vessel for preventing them from being separated; and wherein the medical device also comprises a second locking ring joinable to the vessel, also inserted in the outer case and separate from the first lid and from the vessel; or - the first locking ring is separate both from the first lid and from the vessel for, in use, being joined to the vessel and to the lid after a cornea has been inserted in the vessel. - the first lid is joined to the vessel; and the first locking ring is intact and non-deformed, and is joined both to the first lid and to the vessel for preventing them from being separated; and wherein the medical device also comprises a second locking ring joinable to the vessel, also inserted in the outer case and separate from the first lid and from the vessel; or - the first locking ring is separate both from the first lid and from the vessel for, in use, being joined to the vessel and to the lid after a cornea has been inserted in the vessel.