Saptarshi Mukherjee, M.Optom

Senior Optometrist, Centre For Sight

Director of Advance Studies (India), Vision Science Academy

Vision Science Academy Exclusive

Frequently we are wondering, why can’t we see as well when we drive at night? Although our vision is good as 6/6. It has been found that more than 60% of vehicle accidents happen at night-time in India, due to driver’s visual fatigue and performance, as well as poor visibility in general. ⁽¹⁾ Night driving is riskier than driving during the day, due to increased road hazards, reflection, mesopic pupil conditions that affects our performance to see in ambient light conditions. The accident fatality rate is reportedly three times greater at night than during the day in UK.⁽²⁾

High-beam LED or Xenon headlamps are introduced to enhance light conditions for drivers, but it is one the most common complaints of drivers who have trouble seeing at night when light coming from traffic. Glare can be distracting, pleasant and reduce reflex time.

Uncorrected presbyopia is one of the major causes of inability to see close objects and distance judgement. As it can be avoided in monitoring a safe speed on the dashboard speedometer.

Untreated myopia and astigmatism make it difficult to see objects that are far away, such as road signs, debris, distance, uneven roads, and pedestrians. In astigmatism light is focused on multiple points instead of one which creates a blurry image of street light or headlights. For that reason, drivers cannot judge the depth as well as dynamic motion distance.

Therefore, for safe driving visual acuity as well as visual function is very important. Well maintained Binocular vision, wide visual field, dynamic vision, and contrast sensitivity are playing an important role in safe driving.

Regular eyes check-up and proper refractive correction is very much needed to avoid fatal incidents. Correct and suitable spectacle lens dispensing is also a major fact in these circumstances.

For many decades high contrast lenses like yellow to amber shades have been used to enhance environmental contrast. These types of shades are more effective in foggy weather, dusk and low luminant streets.

Hazardous light which can produce glare, can be cut off by anti-reflective coating. Double sided coated lens is more efficient to neutralise internal reflection. Glare from fog light of oncoming cars is also cut off by polarised lenses. These types of lens or shades are specially made to filter or scatter out blue spectrum.

Few studies have shown that night driving glasses do not improve any night vision.⁽³⁾ Even Yellow tint decreases the amount of entering light which reduces visibility. Night driving glasses slowed down visual impulses which made night vision somehow worse. Any tinted glass reduces the saturation of other colours which would be hazardous. Because whatever we will see will be tinted which will force us to miss any sign, signals and slow down the motion reflexes. All market available tinted glasses are non-prescription lenses which cannot correct the visual acuity.

Driving glass is not only for night driving, but it should also help in daytime to focus better on road signs, street signs, pedestrians even in low lights and maintain motion reflexes. So, driving glass should be added with UV protection which protects eyes from long exposure. Even polarised lenses are also helpful in this condition, especially in daytime.

Our pupil size changes according to light exposing conditions, so specified designed lenses which can reduce peripheral distortion are also available in the market.

We should even clean our glasses before driving to prevent any stains, dirt, or dust on lenses. High performance lens coating makes the lens durable, scratches free and ionised dust. So, we should choose our perfect prescribed lens to enhance our driving skill and safety.

Reference:

1. Pitchipoo P, Vincent DS, Rajakarunakaran S. Analysis of prime reasons for nighttime accidents in public transport corporations. In Proceedings of International Conference on Advances in Industrial Engineering Applications (ICAIEA2014) 2014 Jan 6 (pp. 6-8).
2. https://www.assistprotect.co.uk/Article5.cfm [Last accessed 23 Aug 2023; 09:59pm AEST]
3. Hwang AD, Tuccar-Burak M, Peli E. Comparison of Pedestrian Detection With and Without Yellow-Lens Glasses During Simulated Night Driving With and Without Headlight Glare. JAMA Ophthalmol. 2019;137(10):1147–1153