PurposeThe veracity of claims made by researchers and clinicians when reporting the impact of lighting on vision and other biological mechanisms is, in part, reliant on accurate and valid measurement devices. We aim to quantify the intra-and inter-watch variability of a commercially available light sensor device which has been widely used in vision and other photobiological research. Methods Intra-and inter-watch differences were investigated between four Actiwatch Spectrum Pro devices. The devices were used to obtain measurements on two separate occasions, under three different controlled light conditions; the Gretag Macbeth Judge II lightbox was used to produce Simulated Daylight (D65), Illuminant A (A) and Cool White Fluorescent (CWF) lighting. Results Significant inter-watch differences were noted when considering tricolour (red, green, blue) and the white sensor outputs under each of the three illuminants (p<0.01). A significant interaction was also found between tricolour sensor and watch used (p<0.01). Intra-watch differences were noted for the tricolour and for the white sensor outputs under the three illuminants (≤0.05), for all but one watch which showed no significant intra-watch difference for the white 'sensor output' under the D65 illuminant. Conclusion Use of spectral sensitivity devices is an evolving field. Before drawing causal relationships between light and other biological processes, researchers should acknowledge the limitations of the instruments used, their validation, and the resultant data. The outcomes of the study indicate caution must be exercised in longitudinal data collection and the mixing of watches amongst study participants should be avoided.

Introduction: Direct observation in the radiotherapy clinic remains the primary method for the assessment of procedural skills. But with increasing automation and reductions in clinical placement time during the recent pandemic, the role of summative, simulation-based assessment is being revisited. The aim of this article is to share early experiences of using Virtual Environment for Radiotherapy Training (VERT) in the assessment of a palliative, parallel pair, external beam treatment delivery technique in a new pre-registration undergraduate programme. Methods: Eight first-year students completed a campus-based individual virtual assessment using virtual patient plans representing metastatic disease in the brain and pelvis and late-stage primary lung tumours. Performance was logged on a 25-item checklist for pre and post-procedure checks and treatment delivery tasks. Results: All eight students participated in the assessment with seven students (87·5%) achieving a pass grade at first attempt. The course team observed that participants demonstrated a range of skills and abilities and were able to compare and contrast individual approaches to patient positioning. Specific feed-forward action points were also highlighted as areas for students’ to focus on during their second placement. The project also identified logistical benefits for assessment teams. Conclusions: While these experiences are a single snapshot, a VERT simulation-based summative assessment is feasible and identified benefits included controlled observation and structured feedback on individual performance and scheduling pressure reductions for clinical teams. However, more work is needed to determine the psychometric qualities and predictability of performance in more complex techniques.