The sympathetic nervous system affects the eyes primarily by enlarging the pupils.
When danger or stress activates the sympathetic nervous system, the body prepares for a "fight-or-flight" response. This response has direct effects on the eyes, most notably:
- Pupil Dilation (Mydriasis): The sympathetic nervous system causes the pupils to dilate, allowing more light to enter the eye. This enhances vision, particularly in low-light conditions, and improves the ability to see potential threats or escape routes. According to the reference, the purpose is to "enlarge your pupils to let more light in and improve your vision".
This physiological change is part of the body's broader response to ensure heightened awareness and readiness during stressful or dangerous situations.
