To the Editor.
—Rootman et al, in their recent article in the Archives (1982;100:468-471) entitled "Ocular Absorption and Toxicity of a Radiosensitizer and Its Effect on Hypoxic Cells," have very elegantly shown that the ocular absorption of the desmethyl derivative of misonidazole (Ro-9963) was effective. This radiosensitizer is used to enhance the effect of radiation on malignant cells thought to be radiation-resistant because of hypoxia, and, as an example, the cells in a retinoblastoma were chosen. However, it is possible that these particular cells can be rendered radiosensitive by making them hyperoxic, despite the rather meager retinal blood supply.Usually oxygen levels elevated above normal in the breathing mixtures increase only the dissolved oxygen levels in the blood. Only a small fraction of the total tissue oxygen requirements are supplied by dissolved O2 in liquid blood, which has a low oxygen-carrying capacity, similar to water. For this reason, throughout
Maurice B. Landers, M. L. Wolbarsht. Ocular Absorption. Arch Ophthalmol. 1983;101(1):134. doi:10.1001/archopht.1983.01040010136029