A simple apparatus for controlled rate corneal freezing II.

A corneal freezer without electrical or mechanical function is described. Cooling is achieved by partial immersion of the freezing unit in liquid nitrogen. The cooling rate is controlled by the heat content in the unit and the facility for heat removal from the unit. Corneas are frozen in aluminum vials. Corneas are thawed in less than 30 sec without risk of over heating, when the vials are placed on the metal core of another freezing unit at room temperature.