What is night myopia?

Night myopia is a condition in which eyes become nearsighted in low-light conditions. The cause of night myopia has to do with a refractive error that becomes noticeable when the pupils dilate. Treatment of night myopia includes corrective glasses or contact lenses.

Studies have shown that young adults, particularly teenagers, are at a higher risk of having night myopia.

People with night myopia may find driving at night difficult. Driving with uncorrected night myopia can put you and other drivers at risk.

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Night myopia has been studied since the early 18th century. Though scientists are still working out details, many believe the main cause is related to eye accommodation.

Accommodation is a term used to describe how the eye adapts to different focal points. For example, when you're focused on your phone screen, then look up for a moment, many tiny changes take place in the eye to let you focus at each distance.

One of these changes is that the pupils constrict to focus up close and dilate to focus at a distance. Recent studies discovered that the eyes respond to darkness by using accommodation to focus up close.

Here’s where the problem comes in. Another function of the pupils is to control how much light comes in. They do this by constricting in bright conditions to only allow in as much light as the eyes need. Alternatively, they dilate in dark conditions to let in more light. This function is called dark adaptation and allows you to see at night.

Scientists believe that the eyes may respond to darkness by focusing at an intermediate/near range rather than at a distance. This results in blurry vision when looking far away in the dark. The eyes also respond to darkness by dilating the pupil, which further increases the amount of blur. 

Symptoms of night myopia are similar to those experienced with night blindness. These include:

• Seeing glare or halos around traffic lights

• Discomfort or eye strain when trying to focus in low-light situations

• Finding it especially difficult to see when night driving

• Vision is significantly more blurry at night

• Squinting frequently to try and improve visual clarity

A study was done to measure the relationship between night myopia and nighttime car accidents. It found that people with night myopia were involved in more nighttime accidents than those without. They are also more likely to have these accidents in the future.

As mentioned before, teenagers are more likely to have night myopia than adults. Teenagers are also at a higher risk than any other age group for being involved in a car accident.

With this double whammy of risk, it’s important for teenagers to undergo regular eye exams. This is especially critical before they get their driver’s licenses.

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Research suggests that night myopia is a sign of regular myopia that has not been corrected — the problem just becomes more noticeable at night.

Fortunately, night myopia treatment is as simple as wearing corrective lenses for regular myopia.

Wearing corrective glasses or contact lenses for night myopia can improve visibility and increase confidence when driving at night. [Read our article on night driving glasses.]