Ocular Brachytherapy: Clinical Applications, Procedure, and Efficacy

What is Ocular Brachytherapy? 

Ocular brachytherapy is a localized form of radiotherapy that involves the temporary  fixation of a radioactive source to the eye. 

• The Device: A small, specialized disc known as a plaque (typically  constructed of gold or titanium) is used to house radioactive seeds. ∙ Isotopes: Depending on the tumor’s dimensions and location, clinicians  utilize various isotopes, most commonly Iodine-125, Ruthenium-106, or  Palladium-103. 

• Precision: The gold alloy backing of the plaque serves as a radiation shield,  directing energy inward toward the malignancy while attenuating the dose to  the orbit and surrounding healthy tissues.

Clinical Indications 

While primarily utilized for Uveal Melanoma, this modality is also effective for: 

• Retinoblastoma: The primary intraocular malignancy in pediatric patients.

• Choroidal Hemangioma: A benign but vision-threatening vascular tumor.

• Optimal Candidacy: Ideal outcomes are typically observed in tumors with a thickness $<5$ mm and a basal diameter $<14$ mm.

The Surgical and Treatment Protocol 

The treatment process is a multidisciplinary effort divided into three distinct phases: 

• Surgical Implantation: Under general anesthesia, the surgeon sutures the radioactive plaque to the scleral wall, precisely aligned with the tumor base.

• Radiation Delivery: The plaque remains in situ for 3 to 7 days. During this period, the patient may be monitored in a specialized unit to ensure radiation safety and clinical stability. 

• Explanation: Once the prescribed therapeutic dose is achieved, a second minor surgical procedure is performed to remove the plaque.

Clinical Benefits and Success Rates

Ocular brachytherapy has revolutionized the management of intraocular tumors: 

• High Local Control: Success rates exceed 90% for small-to-medium-sized tumors. 

• Globe Preservation: Unlike enucleation, brachytherapy allows the patient to retain the natural structure and appearance of the eye. 

• Survival Equivalence: Large-scale clinical trials, such as the COMS, have confirmed that survival rates for brachytherapy are statistically equivalent to radical eye removal.

Safety, Side Effects, and Risk Management 

While the procedure is highly controlled, ionizing radiation can impact ocular structures over time. 

• Acute Post-Operative Symptoms: Patients may experience mild discomfort,  a "foreign body" sensation, subconjunctival hemorrhage, or transient diplopia  (double vision). 

• Long-Term Radiation Sequelae: 

  • Radiation Retinopathy/Maculopathy: Vascular changes in the retina.

  • Cataractogenesis: Accelerated clouding of the lens. 

  • Radiation Optic Neuropathy: Damage to the optic nerve. 

  • Secondary Glaucoma: Often linked to tumor resorption or neovascularization.

Recovery and Longitudinal Follow-Up 

The physiological transition from active tumor to inactive scar tissue is a gradual process, typically spanning 3 to 6 months. 

• Immediate Post-Op: Patients are advised to use a nocturnal eye shield for the first 10 days and avoid strenuous activity for 14 days. 

• Return to Function: Most patients resume professional duties and normal activities within 2 to 4 weeks. 

• Surveillance: Frequent ophthalmologic assessments are required—typically every 3–4 months in the first year—to monitor tumor regression and manage any delayed radiation side effects.

Conclusion 

Ocular brachytherapy represents a sophisticated intersection of surgical precision and radiation physics. By providing a curative-intent treatment that prioritizes the patient’s quality of life and visual function, it remains a cornerstone of ophthalmic oncology. Beyond the clinical data, the procedure offers profound psychological benefits, providing patients with a viable path to recovery without the trauma of globe loss.