One of the most common questions our doctors get asked is “why does my eyesight worsen at dusk or dawn?”. The answer has to do with the tiny light-gathering cells at the back of your eyes, located on your retinas.
Many of you have heard of rods and cones. These are the cells that gather light at the back of your eyes, known as photoreceptors. The rods and cones have different jobs. The cones are used for sharp, detailed central vision and are most effective during daylight hours. The rods are located more peripherally in your retinas and are more sensitive in low light levels.
Because the cones need so much light to work well, when the light is weak (such as at dawn or dusk), they can’t register sharp vision. And as the light is changing, the rods are not fully active for “night mode”. So this transition period is most difficult for your eyes to adjust to. This is why so many traffic accidents happen at dusk or dawn.
So remember this when you are driving in the morning or evening – reduce your speed because you are actually not seeing as well as you normally do.