Radiotherapy for age related macular degeneration causes transient lens transparency changes

Aim-Evaluation of potential side effects of photon radiotherapy on the tran sparency of the lens. Methods-The anterior segments of 14 phakic eyes from patients suffering fro m subfoveal neovascularisation as a result of age related macular degenerat ion (AMD) were documented by Scheimpflug photography (Topcon SL-45, Kodak T max 400) before the start of radiotherapy as well as 6 and 12 months afterw ards. All negatives were evaluated by microdensitometry, and peak heights f or distinct layers of the lens were used for statistical comparison. Extern al beam radiotherapy (6 MeV photons) consisted of a total dose of 20 Gy, de livered as 10 fractions of 2 Gy. Results-Six and 12 months following irradiation statistical comparison of t he ratios in density change of lenses from irradiated versus non-irradiated fellow eyes revealed statistically significant (p less than or equal to 0. 05) loss of transparency of layers 5 and 7 of the nuclear region. In layer 1 (capsuloepithelial complex) the changes were close to significance. At th e 12 month examination, however, all of these significant changes had disap peared. Conclusion-Six months following radiotherapy for AMD, both the anterior cap suloepithelial region and the nuclear layers showed precataractous changes. As most of these significant differences had disappeared after 12 months, it is obvious that these findings reflect acute radiation damage to the len s epithelial cells and an ionising effect on the proteins of the lens nucle us. Long term studies will have to be carried out to demonstrate whether or not this acute radiation damage, which is expressed as a transient increas e in light scattering of some layers of the lens, actually does lead to per manent transparency changes, thus reflecting radiation cataractogenesis, an d if so, after what time interval and to what extent cataract occurs.