For many of us our vision at night is worse than during the day. This is called night myopia. It can affect people in varying degrees – some people might notice it a lot and others not at all. We usually notice it the most while we’re driving. Even with our glasses and contacts things might be a little blurry.
Night myopia occurs when the ambient light changes. As the light is decreased, our pupils react by dilating (opening more). This is a natural reflex and not something we can willingly control. The dilation of our pupils is meant to allow more light in because of the dimming conditions, but at the same time the larger pupil creates larger blur circles that are not focused on the retina (back of the eye). In turn, what we try to do to fix this is squint. Squinting reduces the amount of light we let into our eyes and helps to focus the light better. However, it isn’t good for us to be constantly squinting to see better as it can cause eye strain and fatigue.
If night myopia is bothersome, glasses can be prescribed to alleviate the blurry vision. It would only be a slight prescription to bring into focus the light that is out of focus. Also, the glasses would only be used for driving or watching movies. Prescription glasses with the proper coatings can also help with vision while driving in the rain or if you experience problems with glare and headlights. If you already have glasses and still are bothered by the blurring at night, you may want to consider a different prescription for night driving. It is not a good idea to be wearing a higher prescription all the time as it will cause eye strain when not used during the right conditions.