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Remarkable  progress has been made with respect to the visualization of tumors for treatment planning purposes and the application of highly accurate radiation dose delivery. However, it is still inevitable that the eye and optic tract may receive a significant radiation dose that exceeds its normal tissue tolerance dose. Depending on the extent of involvement of the eye and optic tract in the radiation field, variable acute and late ocular damage may occur. Retinopathy and optic neuropathy are relatively common late ocular toxicities of radiation therapy for tumors arising in the brain, head and neck. Both can have important clinical consequences that may contribute significantly to a deterioration of the patient’s quality of life. Patients present mainly with visual symptoms that may include partial or complete loss of vision and visual field defects. Accurate estimation of the prevalence of retinopathy and optic neuropathy after radiation therapy  in patients with brain, head and neck tumors, in relation to the administered radiation dose is lacking. The aim of this study was to systematically review the prevalence of retinopathy and optic neuropathy in patients undergoing radiation therapy for brain, head and neck tumors. Further, we aimed to evaluate the effect of both radiation dose and the patient characteristics on the occurrence of retinopathy and optic neuropathy.

The PubMed, Embase, and Cochrane Library databases were searched for articles reporting the prevalence of retinopathy and optic neuropathy in patients undergoing radiation therapy for brain, head and neck tumors. The primary outcome was the pooled prevalence of retinopathy and optic neuropathy. The secondary outcome consisted of the effect of the total radiation dose prescribed to the tumor on the occurrence of retinopathy and optic neuropathy. Furthermore, we aimed to evaluate the radiation dose parameters to the tumor, retina, optic nerve and chiasm on the occurrence of retinopathy and optic neuropathy.

Seventy- eight publications were selected describing a total of 11279 patients (mean age 51 years and a mean follow-up of 57 months). The pooled prevalence was 3.8%. No retinopathy was reported for a prescribed dose to the tumor that is less than 50Gy (Figure 1). The prevalence of optic neuropathy was higher for a prescribed dose to the tumor at >50Gy compared to a prescribed dose to the tumor at <50Gy (Figure 2).  We observed a higher prevalence rate for retinopathy (6.0%) compared to the prevalence of optic neuropathy (2.0%). Insufficient data on organs at risk dose is reported, making it impossible to establish a more detailed dose-response relationship.

In this systematic review we observed a higher prevalence rate for retinopathy (6.0%) compared to optic neuropathy (2.0%) for patients undergoing radiation therapy for brain, head and neck cancer.  This review emphas the need for future studies considering retinopathy  and optic neuropathy as a primary objective parameter.