Gopinath D, B. Optom
Fellowship in Optometry, Aravind Eye Care System, Chennai, India
Driving is a complex task that requires focus, skill, and patience. You need to make sure all your senses are fully engaged, especially since the eyes play a significant role in it. Sight is the first most sense to drive safely. Even a minor loss of vision can affect your driving and increases the risk of accidents which in-turn endangers people’s lives.
How sight is effectively used in driving (1)
- To Aim High—look ahead, not down. The experienced driver’s attention is focused on the road ahead with his or her central vision following the intended path of travel.
- Keep Your Eyes Moving—a good driver concentrates on selecting details in the traffic scene.
- Get The Big Picture—Search the scene and check the rear-view
In 2017, there were 464,910 road traffic accidents in India and 147,913 fatalities, accounting for an accident every minute and a death every 3.5 minutes.(2) However, over 80% of accidents and fatalities are directly attributable to eyesight difficulty. Perceptual and cognitive functions that impact driver safety and performance include visual functions, auditory skills, biomechanical skills, speed judgment and adaption, reaction time, and attention.
According to the sub-section 3 of section 8 of the Motor Vehicle Act (MVA), a self-declaration (form 1) to drive a non-transport vehicle and a medical certificate from a registered medical practitioner (form 1A) to drive a transport vehicle are the only formal requirements in India. (2)
Self-declaration form 1 carries three questions related to visual function –
- Is the applicant able to distinguish a motor car number plate from 25 meters?
- Is the applicant able to distinguish primary colours such as red and green?
- Does the applicant have night blindness?
The medical examination form carries the same questions to be answered by a registered medical practitioner but does not mandate any specific test or assessment criteria.
To use the eyes effectively, traffic safety visual skills are a must for drivers to detect dynamic and static objects and obstructions while driving. To ensure good eyesight for safe driving, certain basic visual examinations are recommended.
Visual acuity, Vision-specific requirements for driving vary from country to country. Most countries mandate visual acuity of 20/40 in the better eye.
Visual fields, Horizontal visual field of 120° and more on Goldman perimetry or confrontation test are considered as the ability to see objects out of the corners of the road.
Figure 1: Reduced field of vision affecting in driving
[Pic courtesy: GCM Blog. (n.d.). Glaucoma Centre. https://www.glaucomacenter.com/blog]
Depth perception helps detect how far away objects are approaching the road.
Figure 2: Depth perception to help to obtain information on approaching vehicles and obstacles
[Picture Courtesy: Depth perception in vehicle. (n.d.). [Image]. Ransin Injury Lae. https://images.app.goo.gl/LMBYXW4v4QuMXF5P9]
Colour vision defective individuals are those who are not able to identify the basic colours used in traffic signals. People with Colour vision defects are not advised to drive; however, the road transport and highway Ministry has announced that those who had mild to moderate colour can obtain a driving license. (3)
Night vision includes difficulty recovering quickly from the glare of oncoming lights.
Figure 3: Better vision at night helps to reduce the glare
[Picture Courtesy: https://glaucomacenter.com/blogs/utadmin]
Low contrast sensitivity has difficulty in night driving when seeing high beam headlights and Highway sign boards during fog and Rainy. Those who experience Binocular diplopia are not eligible for driving.
Ocular pathologies affecting driving:
There are certain ocular pathological conditions that affect driving. Some of them are,
- Macular degeneration
- Vision changes after systemic diseases such as Diabetics, Hypertension, Thyroid, Stroke, etc.
- Retinitis pigmentosa
- Traumatic conditions
- Dry Eye also impacts quality vision.
There is a term called Conditional Driving License for those who have visual morbidity with compromised visual ability to drive with some limitations such as daylight driving, restriction to a reasonable radius from home, restriction to familiar areas, speed limitation, no highway driving, and more frequent retesting based on the prognosis of the condition. (5)
The most important thing to be addressed is that even a one-eyed person can also get a driving license after 6 months of adaptation to losing vision in one eye by obtaining basic visual requirements as already mentioned above. (6)
In the current era, driving has become a much-needed skill, and everyone starts to drive without proper visual examination, which leads to several vehicle crashes. Vehicle crashes, mainly due to poor vision can be prevented with prior screening while registering for a driving license. Those who did not meet these criteria are referred for further visual examinations it also helps to rule out ocular complications and other systemic diseases.
- Helpful Driving Info | Using your Eyes Effectively. (n.d.). DriversEd. https://driversed.com/driving-information/defensive-driving/using-your-eyes-effectively/ [Last Accessed – 20th Nov 22, 20:45PM AEDT]
- Honavar S. G. (2019). Driving blind – Should tests of visual function be mandatory for driving license? Indian journal of ophthalmology, 67(2), 193–194. https://doi.org/10.4103/ijo.IJO_150_19
- Cole, B. L. (2016). Colour blindness and driving. Clinical and Experimental Optometry, 99(5), 484–487. https://doi.org/10.1111/cxo.12396
- Optical, V. (2020, April 28). The importance of good vision while driving. Visio Optical. https://visiooptical.com/the-importance-of-good-vision-while-driving/
- https://doi.org/10.1111/cxo.12396Vicroads. (n.d.). Vision and driving. https://www.vicroads.vic.gov.au/licences/health-and-driving/vision-impairment [Last Accessed – 20th Nov 22, 20:45PM AEDT]
- Transport Commissioner. (2018, August 21). Driving Licence for differently abled. Chennai; Transport Commissioner Chamber. https://tnsta.gov.in/homepage [Last Accessed – 20th Nov 22, 20:45PM AEDT]