Because a lower-than-optimal amount of light reaches the retina in low-light settings, visual acuity is diminished at night.
Wearing sunglasses at nighttime limits the amount of light entering the retina even more, and is thus not supported under any circumstances — especially when driving at night — because it intensifies darkness-related vision impairment.
Even sunglasses with yellow or clear amber lenses, which are designed to enhance contrast during the day, will work against you at night.
There is, however, one exception…
Wear your shades at night during this “midnight sun” period of the year if you reside in Alaska or near the North or the South Pole when there is constant sunlight near the summer solstice!
How Do Sunglasses Aid Night Vision?
On bright, sunny days, most people are aware that good-quality sunglasses protect our eyes from the sun’s damaging UV rays, minimize glare, and improve visual comfort. However, it is a little-known fact that wearing sunglasses during the day can help with night vision.
According to research conducted by the American Optometric Association (AOA), two or three hours of intense sunlight can delay the initiation of dark adaptation of rod photoreceptors by 10 minutes or more, and in some circumstances, full night vision sensitivity may not be reached for hours. These investigations also found a 50% decrease in visual acuity after 10 days of sunshine exposure, as well as deficits in the visible range and contrast discrimination at night. During daylight hours, wearing dark shades that filter 85 percent visible light was proven to decrease or prevent night vision impairment.
The Transformation From Daylight to Night Vision
Our eyes must undergo a process known as dark adaptation in order to function at their maximum sensitivity in low-light circumstances. The dependence on high-resolution photoreceptor cells in the retina (cones) is shifted to lower-resolution photoreceptors during this phase (rods). Photopigments are found in both cone and rod photoreceptors and are required for vision. Cone cell pigments are activated in bright sunshine, whereas the photopigment in rod cells (rhodopsin) is inactivated or “bleached” which are basically inactive.
According to studies, wearing sunglasses that filter 85 percent of visible light during daylight hours allows for faster dark adaption and prevents night vision loss.
The Importance of Dark Adaptation
The most dangerous period to travel, according to the Insurance Institute for Highway Safety, is between 5 and 7 p.m. At this time of day, there are more roadway deaths than at any other time of day.
Drivers must contend with changing light conditions as well as a significant number of vehicles on the road during this evening “rush hour.” When the sun is low in the sky, it can generate a lot of glare, which makes seeing difficult. Drivers’ eyes must adjust to low-light situations and incoming headlights after dusk. Many car accidents that occur at this time of day may possibly be avoided if more individuals wore sunglasses during the day.
This would allow drivers’ eyes to adjust more quickly to decreased ambient light, allowing them to see and react more quickly after the sunsets. Wearing dark sunglasses throughout the day is even more crucial after the age of 50 because our eyes’ capacity to adjust to changing light situations deteriorates with age. This is true not only for night driving but also for things like visiting a dimly lit restaurant or a dark theater. The ideal sunglasses for protecting night vision during the day should filter 100% UV rays and around 85% visible light.