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To the Editor:
In the recent flurry of interest in ophthalmic cryosurgery there have been a number of probes designed to apply low temperature to ocular tissues. In most of these devices the coolant is circulated through a hollow probe and therefore represents no problem of sterility. In at least two instances that we know of, workers have experimentally used solid metal probes directly immersed in a bath of liquid nitrogen. We have cultured liquid nitrogen and have isolated microorganisms, including hay bacillus (eg B subtilis) and Staphylococcus albus. We then inoculated liquid nitrogen with S aureus and Fasarium solani and both organisms were recovered by culture. Liquid nitrogen is not self-sterilizing, and should be used with care. This is to be expected when one considers that liquid nitrogen is made by condensing nonsterile air.
Hilton GF. ASEPSIS AND CRYOSURGICAL PROBLEMS. Arch Ophthalmol. 1965;73(4):607. doi:10.1001/archopht.1965.00970030609041