The Joule Thomson principle and expanding carbon dioxide gas is utilized in the construction of a retinal cryopencil. Tip temperatures between -60 C and -70 C are maintained anywhere on the globe, and absolute reduplication of lesions can be produced by the constant freezing capacity inherent in this system. Cooling rates in excess of 50 C per second with an automatic defrost system and a thawing time of less than three seconds are generated in a small easily handled probe. The probe-contact diameter is only 2.5 mm. No drop of cooling efficiency occurs during surgery because a constant gas pressure is maintained. Probe temperature can be regulated between -70 C and -40 C. The system has proved very satisfactory in the treatment of retinal breaks with and without detachment as well as in the treatment of retinal tumors.
Amoils SP. The Joule Thomson Retinal Cryopencils. Arch Ophthalmol. 1968;80(1):128-131. doi:10.1001/archopht.1968.00980050130021