Aim To report the results of whole anterior segment proton beam radiotherapy (PBR) for diffuse iris melanoma.

Methods Between 2000 and 2011, 12 patients with iris melanoma received PBR to the entire iris and ciliary body.

Results Patients had a mean age of 57 years and a median follow-up of 3.5 years (range 1–11.6 years). Tumour iris involvement was 1–4 h in five patients, 5–8 h in four and 9–12 h in three. Angle involvement was 6–8 h in five patients and 9–12 h in seven. The visual acuity (VA) before treatment was 6/5–6/6 in six patients, 6/8–6/9 in three and 6/18–6/38 in three. No tumour recurrence occurred during the follow-up period. Glaucoma treatment was required in 11 of 12 patients. The visual acuity at the last follow-up was 6/5–6/9 in five patients, 6/18–6/24 in three, 6/60–1/60 in two and no light perception in two. Four patients developed varying non-severe degrees of limbal stem cell deficiency, which was treatable with conservative measures.

Conclusions Whole anterior segment PBR is a useful alternative to enucleation for diffuse iris melanoma. Most patients will need treatment for glaucoma and some may require treatment for tear-film instability and/or stem cell failure.