Orbital cavernous venous malformation shrinkage during fractionated stereotactic radiotherapy contributing to the development of radiation retinopathy.

Background: Posterior movement of ocular tissue secondary to orbital cavernous venous malformation shrinkage from fractionated stereotactic radiotherapy can allow healthy structures to move into the radiation field during treatment. This may carry an increased risk of radiation-induced retinopathy.

Methods: We present a case of a young female whose radiotherapy treatment for an orbital cavernous venous malformation resulted in a 3 mm reduction in proptosis and subsequent retinopathy.

Results: The severity of the patient's radiation-induced radiotherapy exceeded expectations. The venous malformation shrinkage during treatment and ensuing posterior movement of the globe suggested an increased involvement of ocular tissue in the radiation field, prompting consideration of interval neuroimaging and tumour mapping.

Conclusions: We describe and suggest a protocol of onboard neuroimaging during the radiation therapy course to better target tumour volumes and minimise collateral tissue damage. To our knowledge, this has not been previously described in the ophthalmic literature.