Plaque brachytherapy has become the mainstay of treatment for choroidal melanoma after the Collaborative Ocular Melanoma Study (COMS) publications. An understanding of the common complications of therapy and treatments is required for those providers that treat these patients.
Radiation retinopathy is most commonly associated with high radiation dose, proximity of tumor to the macula, and comorbidities such as diabetes or hypertension. The risk of this varies greatly by location, from 5-6% in tumors with less proximity to near 100% in tumors located on the macula. The most common treatments are panretinal photocoagulation, vitrectomy, and observation.
Radiation damages the enzymes that protect the lens, leading to cataract formation. This occurs in 65-90% in anterior tumors and 15-20% for posterior tumors. Patients respond well to standard cataract surgery.
Neovascular glaucoma (2-15% in most series) can potentially result from melanoma-induced angiogenic factors along with retinal ischemia from irradiation. These cases are difficult to manage and refractory to most therapy.
Vitreous hemorrhage (5-year risk ~15%) and retinal detachment (1-2%) are generally secondary to the tumor itself, but may also occur due to proliferative radiation retinopathy. Vitrectomy is required for treatment.
Radiation plaque placement can disrupt extraocular muscle insertion sites and the blood supply to the extraocular muscles (< 5% incidence in modern series). The radiation itself can also damage the muscle fibers at an ultrastructural level, leading to strabismus. Patient may require extraocular muscle recessions and resections to straighten the eyes.
Necrotizing effects of radiation therapy and local inflammation can lead to necrosis of the sclera, an outer coating of the eye. This occurs in 5% or less of patients.
