Anterior segment complications after helium ion radiation therapy for uveal melanoma. Radiation cataract
W. J. Meecham, D. H. Char, S. Kroll, J. R. Castro and E. A. Blakely
Department of Ophthalmology, University of California, San Francisco.
OBJECTIVE: To delineate the factors in the development of visually
significant cataract after helium ion irradiation of eyes with uveal
melanomas. DESIGN: Retrospective analysis with multivariate analysis using
life tables and Cox proportional hazard models in addition to other
nonparametric techniques. PATIENTS: All patients with a noncataractous
other eye and adequate dosimetry data who were treated with helium ion
irradiation. RESULTS: Significant cataracts (grade 3+ or 4+ on a 0 to 4+
scale) developed in 129 patients (44%). The risk of cataract development
peaked at 3 years (25% per person-year) and then declined to a sustained
level of 7% to 9% per year after 7 years. In multivariate analysis, the
percentage of lens included in the treatment port was the predominant
predictive correlate with time to significant cataract (relative risk of
2.97 for a 25% increase in the percentage of lens in the treatment port).
Patient age, preexisting cortical opacity, and ultrasound tumor height were
also significant; ciliary body involvement and tumor dose had smaller
effects. Kaplan-Meier analysis demonstrated an increased rate of
cataractogenesis with each increment of the percentage of lens in the
treatment port; when more than half of the lens was in the beam, the risk
of cataract exceeded 90% within 7 years. CONCLUSIONS: Cataract development
after helium ion irradiation is a function of the amount of the lens in the
beam. Unlike neovascular glaucoma that develops mainly in the first few
years after treatment, cataract continues to develop during the entire
length of follow-up.
