Can navigation lights mounted on my own watercraft impair my night vision?
Seasoned mariners are well aware that the only way for a vessel′s operator to see in the dark, whether under moonlight or in extremely dark conditions, is to prevent any and all
rays of light from being directed into one′s eyes.
On a dark night, even the light of a candle flickering behind you, casting the faintest glow on your bow′s surface, will reflect light back into your eyes and will impair your ability to see in the dark.
The iris in each eye controls an opening (the pupil), finely tuned to open wide in the dark, maximizing the number of rays of light capable of reaching the retina. Light arriving directly (from a light source) or indirectly (reflected off of a surface) toward you that exceeds ambient lighting (moonlight, starlight) will cause the iris to reduce the diameter of your pupil.
If your iris reduces the amount of light reaching the retina in response to an onboard light source, you may not be able to see potentially hazardous objects such as floating logs, buoys, ropes, tow lines, fishing lines and possibly even unlit vessels that otherwise would be illuminated sufficiently by moonlight, starlight or other extremely faint sources of light.