Response of the normal eye to high dose radiotherapy.

Radiation therapy of tumors near the eye or optic nerves often requires incidental irradiation of these structures, even when they are not clinically involved by tumor. Depending on the radiation treatment volume and dose required, radiation injury to the lens, lacrimal apparatus, retina, or optic nerve may result. The time to expression and severity of injury are dose-dependent. This paper reviews the results of 157 patients who were followed for a minimum of 3 years after radiotherapy for primary extracranial tumors at the University of Florida, in which the lacrimal gland, lens, retina, and/or optic nerve(s) received irradiation. This review shows that, after treatment at approximately 1.8 to 2.0 Gy per fraction, the incidence of severe dry-eye syndrome, retinopathy, and optic neuropathy appears to increase steeply after doses of 40, 50, and 60 Gy, respectively.