External beam radiotherapy for age-related macular degeneration causes transient objective changes in tear-film function.

Abstract

Dry-eye symptoms have been described as possible radiation side effects after external beam radiotherapy for age-related macular degeneration. We therefore investigated tear-film function before and after treatment. Thirty-nine patients with no apparent history of dry-eye symptoms were treated with a 6 MV linear accelerator using a 2x2 cm lateral field angled 10 degrees posteriorly. A total dose of 20 Gy, divided into 10 fractions of 2 Gy and administered 3 times a week, was delivered. Before and 1, 3, and 6 months after radiotherapy, tear secretion was measured by means of tear-film fluorophotometry. The fellow eyes served as controls. At baseline, mean tear secretion as measured by tear-film fluorophotometry was 7.15 microl/min in the eyes receiving radiation and 5.89 microl/min in the control eyes. No statistically significant differences were found between the two eyes at baseline (signed rank test). One month after treatment, again no significant differences could be found between the two eyes; 3 months after radiation, however, tear secretion was significantly lower in the irradiated eyes than in the fellow eyes (P=0.0017). Six months after treatment this effect could no longer be detected. External beam radiotherapy using 20 Gy in 10 fractions and a 2x2 cm lateral field causes a statistically significant difference in tear secretion 3 months after radiation. This effect seems to be transient, as it had disappeared in later follow-up examinations.