Ocular complications of high-dose radiotherapy.

The paper by Parsons et al summarizes in elegant detail basic data on the risks involved when radiation therapy is used for tumors near the eye or optic nerves, whether these structures are incidentally irradiated because of proximity of the tumor, or are clinically involved within the volume being reirradiated because of tumor extension. The authors define the influence of radiation treatment volumes and doses required, as well as the potential injury to critical structures within the orbital contents. Clearly, the expression and severity of injury are dose dependent. The data submitted by the authors clearly define the influence of fractionation, fraction size, volume of tissue irradiated, and total dose to that volume on the incidence of severe dry eye syndrome, retinopathy, and optic neuropathy. The most important point is the fact that the incidence of these complications begins to increase steeply after doses of 40, 50, and 60 Gy, respectively.