Night Driving & Vision

  • 5 July 2016
  • Troy Cassidy

In the shorter daylight hours of winter, many of us find ourselves driving in the dark more than at other times of the year. Difficulty with night driving is one of the most common problems that our clients report to us, and no wonder.  Rapidly changing light levels, limited field of vision from our headlights, and glare from bright lights combine to make night driving a visually challenging task.  

The simple fact is that night driving is difficult.  There's no magic way to make night driving as relatively easy as driving on a nice bright day, with the high contrast, stable light levels, good peripheral lighting, and normal colour vision that we enjoy in daylight.  There are a few things we can control, however, which can help to make the best of a demanding task.

1. Reduce Glare

A major cause of glare is light from a bright source, such as car headlights, striking cloudy media.  This causes light scatter, resulting in glare.  Dirty windscreens and smudgy spectacle lenses are the main culprits here.  Keep your windscreen nice and clean, including removing the film that forms on the inside of the windscreen.  A vigorous rub with  a scrunched up newspaper works remarkably well in removing this film.  Keep a chamois or microfibre cloth in the car to maintain clarity on the road.  Similarly, keep your glasses clean with a good lens spray and microfibre cloth, both available from Cassidy Eyecare. 


2. Maximise Dark Adaptation

In low light, our eyes adapt by both opening the pupil to admit more light into the eye, and increasing the amount of light-sensitive pigment in our retinas.  These two factors mean bright lights can cause discomfort, and diminish the dark-adapted state our visual system is trying to maintain.  Always keep your gaze to the left of oncoming headlights, and track the approaching vehicle with your peripheral vision.  This both reduces glare and helps with dark adaptation - looking directly at bright lights will make it more difficult to adjust to the darkness after they pass by.  Keeping the dashboard lights dim is also helpful in maintaining dark adaptation.


3. Keep Your Glasses Up-to-Date

Obvious advice from an optometrist, but valid and important nonetheless.  At night our pupils dilate to allow more light to reach the back of the eye.  This also increases our sensitivity to blur, similar to opening the apeture of a camera.  A slightly out-of-focus image may not be problematic during the day due to smaller pupils and better contrast masking the blur, but can become significant at night.  A correct prescription, combined with a good quality anti-reflective coating, is important for comfortable night driving vision.


4. Check Your Vehicle

There are a few tweaks that can be made to improve the user-friendliness of your car for night driving.  New wiper blades can be an inexpensive way to keep the windscreen nice and clear.  An auto-electrician may be able to recommend headlight bulbs with increased light output, and also ensure that they are aimed appropriately.


Finally, take it easy out there :).  


About Troy Cassidy

Troy graduated from the University of Auckland Optometry programme in 1995, and has worked in optometry practices in NZ, Australia & the UK since then. Along with wife Stephanie, he has owned and operated Cassidy Eyecare in west Auckland since 2010.

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