External radiotherapy

External radiotherapy involves the delivery of high energy beams from a source outside the body to focus them precisely and destroy and heal tumoral lesions. 

There are three different kinds depending on the type of radiotherapy: electron beam radiotherapy, accelerated proton beam therapy (teletherapy) and gamma radiation therapy. 

In ophthalmology, external radiotherapy is mainly used to treat tumours located in the orbit and radiosensitive intraocular tumours like uveal melanoma, vascular tumours of the retina and choroid and childhood retinoblastoma.

In all cases, a team-based approach with specialist ophthalmologists and radiation oncologists is required. The equipment that emits this radiation is very sophisticated and, after a thorough topography of the lesion and specific calculation of the dose to be administered, various sessions or cycles of radiotherapy are given.  

In all instances, a personalised mask is used to secure the head and prevent radiating other parts of the body. 

The results are not immediate and it is essential to wait a few months to determine the effect of the treatment. Check-ups are performed by the ophthalmologist and radiotherapist with a physical examination and imaging tests such as an ultrasound and/or MRI.

External radiotheapy can have side effects on the eye surface like losing eyelashes, reactive conjunctivitis and symptoms of dry eye which can usually be relieved with topical treatment. 

Radition of tumours near the optical nerve poses the potential risk of causing radiation-induced neuropathy and a gradual loss of vision over the medium-term.