Dear Dr. Viki...
Updated: Feb 12, 2020
I am 25 years old and moderately nearsighted. I am able to see very well with my glasses at all times except when I drive at night. Why do I experience such disabling glare?
Many people experience glare with nighttime driving. It is normal for pupils to become larger in dark conditions. Although a larger pupil allows more light into the eye, it is not necessarily well-focused.
During the day, light travels through a smaller pupil and is bent minimally. Light passes through the central aspect of the eye’s lens and comes to a focus at one single point at the back of the eye. As the pupil enlarges at night (younger people have larger pupils), light will pass through a larger opening, thus encountering more lens surface. The lens of the eye is fatter in the middle than on the sides causing light to be bent at many different angles. Instead of one clear point of focus at the back of the eye, there are several focal points in the eye. Having more than one focal point in the eye causes glare.
Ways to minimize glare at night include wearing an up-to-date glasses prescription with anti-reflective coating. Sometimes, turning on the small light of the rear-view mirror helps to make a driver’s pupils smaller minimizing glare.
New symptoms of glare in later life can often be a sign of cataracts. Your eye doctor can help evaluate symptoms and test vision under glare conditions to simulate what you might be seeing while driving.