Your eyes are not the only part of your vision system. Your brain must process the image your eyes send. A recent review looked at thirty-nine studies to see what changes this brain signal over time. The signal is called P100. It measures how fast your brain reacts to light. The review found that this reaction time gets faster as you grow up. It stays steady in early adulthood. Then it slows down after age forty. This slowing is a natural part of getting older. It is not a disease. But it is real.
Other factors also change the signal. Looking through blurry glasses makes the brain take longer to react. Drinking alcohol right before the test also slows the reaction. Coffee had no big effect. Being taller or having a bigger head made little difference. Having one eye stronger than the other did not matter much. Some health issues like diabetes can also slow the signal in some people.
This review is a scoping review. It looks at many different studies. The studies used different methods. This mix makes it hard to say exactly how much each factor matters. Still, the main message is clear. To understand your vision test results, doctors must consider your age, your eye clarity, and what you drank recently. Ignoring these things can lead to wrong conclusions about your eye health.