Background Night battle is an important part of modern warfare. However, dramatically decrease of visual function on low-light environment brings great difficulties to the helicopter medical rescue at night. The use of night vision goggles (NVGs) to assist night battlefield helicopter rescue is a trend in recent years, which is also an effective way to improve the military medical support capability.

Objective To understand the usage of NVGs and the training condition of the helicopter crew, and provide support for constructing and implementing night battlefield helicopter medical rescue courses using NVGs.

Methods Using a self-designed questionnaire, a survey was conducted on NVGs users from helicopter crew members who went to a certain rehabilitation center from August 2020 to April 2021. The survey covered three aspects: (1) Knowledge of night vision (7 items, including, physiological blind spot in night vision, night visual acuity, color vision, night myopia, details identify, scanning techniques, scotopic vision protection); (2) Extent of the impact of NVGs limitations (13 items, including, field of view, distance judgment, color vision, depth perception, visual acuity, target discovery capability, stereo perception, motion perception, asthenopia, neck fatigue, eye pain, headache/dizzy); (3)Training experience of the users.

Results We received 51 validated questionnaires with a recovery rate of 94.4% (51/54). All the cases were male, with a mean age of 36.29 ± 6.37 (range, 25-48) years. Among the 51 NVGs users, 19.3% of them correctly answered 7 questions of night vision. The item with highest accuracy rate was "naked eye visual acuity decreased at night", accounted for 47.1%, while item with lowest accuracy rate was "night myopia and mesopic vision scan technique", accounted for 0. The NVGs users believed except afterimage, the other 12 limitations of NVGs affected them significantly. The impact of decreased distance judgment, decreased color vision and visual field constriction were greatest, and the impact of headache, dizzy and eye pain were smallest. Totally 76.5% NVG users attended training course. The highest number of users, accounting for 94.9%, received training on the method of use, while the fewest, making up 5.1%, received training on dark vision protection.

Conclusion At present, the usage time and frequency of NVGs by helicopter crew members are relatively short. Standardized training for NVGs has not been carried out. Distance judgment, decreased color vision and visual field limitation are key points of the curriculum of night battlefield helicopter medical rescue.