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In the Dark

19 Jan 2017 << back to list

Most of us are aware that driving at night is more challenging than driving in the daytime. We make natural compensations for this as we drive but it is a fact that more road accidents happen at night than during the day.

Road lighting levels at night are noticeably reduced compared to those found by day. This has the effect of enlarging the pupil of the eye more than under brighter conditions. The enlargement in pupil size can emphasize any current slight flaws in focusing, causing blur. If you become aware of this, it is likely your current glasses or contact lenses need altering or an optical correction may be required.

Even if the glasses are correct, it is still common to suffer with glare, and this is often due to light being scattered as it passes through to the back of the eye.

There are four potential media that can cause a problem:

1. The windscreen, inside and outside

2. Glasses or contact lens surfaces

3. The cornea (the window on the front of the eye)

4. The lens inside the eye

Dirty windscreen surfaces can cause an uncomfortable star burst effect. Even if it appears to be clean the back surface can have a thin layer of condensation which degrades the image quality. Likewise dirty spectacles can have a similar effect. It is  advisable therefore to always give your windscreen and glasses a wipe before driving at night. Moreover, reflections from the surfaces of spectacle lenses can frequently cause multiple headlight images. If you become aware of these, look into getting more effective reflection free lenses.

For most of us the cornea remains clear throughout our lives. However untreated glaucoma can cause it to become temporarily opaque. This is because the increased pressure within the eye that typifies glaucoma reduces the efficiency of the corneal chemical pump that normally keeps it clear, allowing water to seep in. This causes a halo effect around street and headlights and needs further investigation. It returns to normal following treatment.

The lenses inside the eyes are where most problems occur. When we are young they are normally completely clear, but over time they become yellow and the efficiency of the light transmission drops. Ultimately this becomes a cataract, but in the early stages the effect is to scatter light from the blue end of the spectrum , causing discomfort when in sunlight as well as with headlights at night.

Generally spectacles cannot change this, however some people have found that a very light brown tint reduces the glare. Any tint also reduces the amount of light from the side of the road as well which is why it is illegal to drive at night with glasses that are too dark.

Some people use amber or yellow tinted lenses but there is no proof that these lenses boost vision on the road and in fact, tinted lenses may worsen your sight. Windscreen tints have an equivalent effect and this is why the Highway Code urges drivers to refrain from using any kind of tint at night.

Our Top 10 tips to ensure your sight is the best at night:

  1. Get your eyes examined regularly (An eye examination is recommended for most every two years).
  2. Check that you’re wearing an up-to-date pair of distance spectacles or contact lenses. 
  3. If possible, keep a backup pair in the car.
  4. Refrain from using tinted lenses but sure that they are reflection free.
  5. Clean the windscreen routinely, inside and out.
  6. Ensure your car’s lighting is working efficiently. Sometimes the lights can be misaligned so make sure they are pointing correctly. Also as the car ages the plastic light covers discolour. You can clean them with a headlight polish kit.
  7. Never look directly at oncoming headlights.
  8. Dim the instrument panel lights, and turn off any interior or map lights.
  9. Clean the front of the windscreen with newspaper, and the inside with a microfibre cloth. Never use your hands as they will leave a grease smear which will cause glare.
  10. Clean the mirrors and angle them so that headlights do not reflect directly in to your eyes.

If you have any problems, for more information please speak to a team member.


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