Which of the following will contribute to a decrease in night vision efficacy?

• A. Nicotine use
• B. Alcohol consumption
• C. Bright light exposure at night
• D. Caffeine intake

Answer: (A)

Night vision hinges on rod cells in the retina and the eye’s ability to dark-adapt. Nicotine stimulates the sympathetic system, leading to pupil dilation and retinal vasoconstriction, which can reduce retinal oxygen delivery and blunt the rod-driven dark adaptation needed for seeing in low light. This combination directly compromises nocturnal visual performance, making night vision less effective. While alcohol and sudden exposure to bright light at night can also disrupt dark adaptation, nicotine’s vascular and neural effects specifically contribute to a greater, more persistent decrease in nocturnal vision. Caffeine tends to increase alertness and does not reliably impair night-vision performance.