Abstract
BackgroundWe observed visual sensations (VSs) in patients undergoing intensity modulated radiotherapy (IMRT) of the brain without the beam passing through ocular structures. We analyzed this phenomenon especially with regards to reproducibility, and origin.Methods and FindingsAnalyzed were ten consecutive patients (aged 41-71 years) with glioblastoma multiforme who received pulsed IMRT (total dose 60Gy) with helical tomotherapy (TT). A megavolt—CT (MVCT) was performed daily before treatment. VSs were reported and recorded using a triggered event recorder. The frequency of VSs was calculated and VSs were correlated with beam direction and couch position. Subjective patient perception was plotted on an 8x8 visual field (VF) matrix. Distance to the orbital roof (OR) from the first beam causing a VS was calculated from the Dicom radiation therapy data and MVCT data. During 175 treatment sessions (average 17.5 per patient) 5959 VSs were recorded and analyzed. VSs occurred only during the treatment session not during the MVCTs. Plotting events over time revealed patient-specific patterns. The average cranio-caudad extension of VS-inducing area was 63.4mm (range 43.24-92.1mm). The maximum distance between the first VS and the OR was 56.1mm so that direct interaction with the retina is unlikely. Data on subjective visual perception showed that VSs occurred mainly in the upper right and left quadrants of the VF. Within the visual pathways the highest probability for origin of VSs was seen in the optic chiasm and the optic tract (22%).ConclusionsThere is clear evidence that interaction of photon irradiation with neuronal structures distant from the eye can lead to VSs.
Highlights
There is a long history of reports of visual sensations (VSs) caused by radiation, under various circumstances [1,2,3,4]
There is clear evidence that interaction of photon irradiation with neuronal structures distant from the eye can lead to VSs
VSs were reported by astronauts during the Apollo mission space flights [5,6,7,8,9,10,11]; it was suggested that Cherenkov radiation [12] or direct interaction of radiation particles, as protons, heavy ions or neutrons with the retina were responsible [13,14,15,16,17,18,19,20,21]
Summary
There is a long history of reports of visual sensations (VSs) caused by radiation, under various circumstances [1,2,3,4]. Even though one might have the impression that occurrence of VSs is completely understood, especially with regards to their origin, this is not the case. We observed VSs in a patient undergoing stereotactic IMRT for a single brain metastasis under circumstances in which direct interaction with the retina was improbable [22]. We observed visual sensations (VSs) in patients undergoing intensity modulated radiotherapy (IMRT) of the brain without the beam passing through ocular structures. We analyzed this phenomenon especially with regards to reproducibility, and origin.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
