Should visual function tests be mandatory for a driving license?

My eyesight’s gone, my reflexes are shot, and I can’t stay awake, but thank God I can still drive. - Robert Breault

Road traffic accidents (RTA) continue to be a major public health problem, with over 1.3 million fatalities and 20-50 million non-fatal injuries and permanent disabilities.[1] RTA is currently the third major cause on the World Health Organization’s list of Global Burden of Diseases.[2] India contributes to 11% of RTA in the world – a gross asymmetry considering that India has only 1% of all motor vehicles on road.[3] India also has the dubious distinction of having the second-highest number of RTA globally and the highest number of deaths. In 2019, there were 4,49,002 RTA in India and 1, 51,113 fatalities, accounting for an accident every minute and a death every three minutes.[3] The total estimated socioeconomic implication of RTA in 2018 was Rs 1,47,114 crores or 0.77% of India’s GDP.[3] Although the causes for RTA are multifactorial, over 95% of accidents and fatalities are directly attributable to human error.

Driving is a complex act that requires possession and recruitment of optimal visual functions, auditory and, biomechanical skills, speed judgment and adaption, reaction time, and attention.[45] Suboptimal cognitive, executive, and physical functions can predispose to RTA.[6] Visual functions contribute to about 90% of sensory inputs essential for safe driving and hence, are the necessary estimable parameters to objectively evaluate potential driver safety.[7]

Poor vision is unquestionably linked to an increased risk of RTA. Drivers with visual impairment are twice more likely to be involved in RTA as compared with those with no visual impairment.[8] Using simulation experiments, it has been demonstrated that patients with advanced glaucoma had a higher risk (80%) of collisions than normal subjects (26%).[9] A study conducted by the Indian Institute of Science found that 81% of drivers who had at least one visual function defect were involved in an RTA.[10] Some important recent data are emanating from screening studies conducted by several non-Government organizations. Mission for Vision screened 15,000 drivers across 12 states of India, 40% of whom were found to have uncorrected refractive errors. Vision Spring found that 68% of the 30,000 screened commercial vehicle drivers in India never had an eye test done, and 60% had an uncorrected refractive error. One in four of those commercial vehicle drivers in the study could not see signs at a 20-30m distance.[11]

A recent meta-analysis has found that the prevalence of vision impairment among drivers in low- and middle-income countries ranged from 1.2-26.4%, color vision defects from 0.5-17.1%, and visual field defects from 2-37.3%. The number of drivers who had received licenses without vision testing ranged from 10.6 to 85.4%. There was a 46% greater risk of RTA among those with visual impairment and a 36% greater risk among those with defective color vision or visual field.[12] A study in this issue of the Indian Journal of Ophthalmology reports refractive error in 15.7% of commercial drivers - hyperopia in 8.2%, myopia in 5.3%, and astigmatism in 2.1%. Presbyopia is reported in a majority (55.8%) of the drivers. Defective stereopsis is seen in 27.4% and color vision deficiency in 3.9%.[13] A study by Kumar et al. found that 28.8% of commercial taxi drivers had an uncorrected refractive error with only 40.9% spectacle compliance.[14] The risk of RTA was twice as much in those with uncorrected refractive error as compared to the emmetropes.[14] Other studies have shown that drivers in India have significant visual morbidity with the attendant risk of RTA.[1516]

Visual acuity is only one of the several predictors of driving safety.[717] Visual fields, color vision, contrast sensitivity, night vision, glare sensitivity, useful field of view, stereopsis and diplopia also have an impact on driving safety, and all these components can be objectively assessed.[717] However, visual function requirements for driving vary globally, and most of the parameters are not part of the formal assessment of visual function for driving license with the excuse that there are no large-scale studies establishing their role in driving safety. Most countries have only visual acuity and visual fields as assessment parameters. Regulatory compliance on part of the driving license applicants seems to be a major barrier. An earlier study in the Indian Journal of Ophthalmology had shown that the legal license renewal procedure was bypassed by 45% of patients with glaucoma, none were asked about their visual fields during renewal, and only 10% of those medically certified were examined by an ophthalmologist, and 44% experienced driving difficulties. Importantly, 30% of those who got a driving license would not have satisfied the International College of Ophthalmologists (ICO) Vision Requirements for Driving Safety guidelines.[18]

In India, a driving license is issued by the Regional Transport Office in each state and the procedure is regulated by the Motor Vehicle Act (MVA) 1988. The MVA was amended in 2017 and the sub-section related to color vision was further amended in 2020.[19] As per sub-section 3 of section 8 of the amended 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 and for all new/renewal applicants aged above 50 years are the only formal requirements.[19] The 2020 amended self-declaration form carries two questions related to visual functions – 1. Is the applicant able to distinguish a motor car number plate from 25 m. 2. Does the applicant have night blindness?[20] The medical examination form carries the following questions to be answered by a registered medical practitioner using his “judgment” or “opinion” but does not mandate any specific test or assessment criteria: 1. Does the applicant, to the best of your judgment suffer from any defect of vision? If so, has it been corrected by suitable spectacles? 2. In your opinion, is he able to distinguish with his eyesight at a distance of 25 m in good daylight a motor car number plate?; and 3. In your opinion, does the applicant suffer from night blindness?.[20] The declaration by the medical practitioner includes the following statements: 1. I certify that while examining the applicant, I have directed special attention to his/her distant vision; 2. I certify that I have personally examined the applicant for reaction time, side vision, and glare recovery (applicable in case of persons applying for a license to drive goods carriage carrying goods of hazardous nature to human life); and 3. I certify that the applicant’s color vision has been tested using a standard Ishihara chart and the applicant has not been found suffering from severe or total color blindness.[20]

Unfortunately, the MVA or any of its amendments do not include objective criteria for the measurement and stratification of visual functions such as testing conditions and quantification for visual acuity and visual fields. Peripheral visual fields should ideally be quantified using Goldmann III4e or Humphrey 120 points screen. While Ishihara chart has been prescribed for color vision testing, the interpretation of the same has been left open to doubt. There is no standard classification of mild, moderate, severe, and total color vision deficiency (as mentioned in the MVA amendment of June 2020) using the Ishihara chart. If the expert group set up by the Government did suggest such a classification, then the objective criteria governing the same should be clearly stated. There are no set criteria for testing and reporting reaction time, “side vision” and glare recovery prescribed in the MVA. The MVA rules purportedly coming into force from July 2022 are likely to do away even with the requirement of a formal driving test by allowing certificates issued by accredited driving training institutes as qualifications enough to procure the license. This step, while simplifying the process of issuing a driving license, is likely to further dilute the standards of assessment of visual standards for driving.

Considering that visual functions are one of the important determinants of driving safety and hence, the incidence of RTA, it is strongly recommended that the MVA be amended to include mandatory vision-specific criteria for a driving license and that qualified ophthalmologists should issue the certificate conforming to the set visual standards. Based on the ICO Vision Requirements for Driving Safety guidelines,[17] an unrestricted driving license could be provided to those with the best-corrected visual acuity ≥20/40 in the better eye with horizontal visual fields of 120° or better. Those with best-corrected visual acuity <20/40 to 20/200 in the better eye with horizontal visual fields of 120° or better may be allowed restricted non-occupational, non-commercial, non-transport personal driving license. Those with visual acuity <20/40 to 20/200 in the better eye but failing the visual fields criteria may not be permitted to drive or considered for a restricted driving license upon a detailed assessment and a driving test. ICO-suggested driving restrictions include limitation to daylight driving, restriction to a reasonable radius from home, restriction to familiar areas, speed limitation, no highway driving, and more frequent re-testing based on the prognosis of the condition. Those with visual acuity <20/200 in the better eye may not be permitted to drive. Monocular patients already have prescribed visual function standards for driving license – visual acuity of 20/40 in the remaining eye, the horizontal visual field of 120o, and a monocular adaption period of 6 months. Apart from baseline screening, every driver involved in a cognizable road traffic accident should ideally have visual functions reassessed by an ophthalmologist. Table 1 summarizes the recommended international, current Indian, and proposed Indian visual function parameters for driving safety.

Table 1

Driving safety parameters - International, existing Indian, and recommended Indian standards

Parameters	Specifications	International Council of Ophthalmology- recommended Vision Requirements for Driving Safety	Current Indian Standards	Recommended Indian Standards*
Visual Acuity measured using standard self- illuminated or projection Snellen Chart	20/40 or better	No visual acuity-based objection to an unrestricted driving license	Ability to read a number plate at 25m distance in good light, (approximately 20/40 to 20/60) by estimation of a medical practitioner, no objective assessment of visual acuity	Unrestricted license
	<20/40 to 20/200	Individual consideration may result in restrictions or denial. Evaluation should include visual and non-visual factors and a road test when in doubt.	No specific stand	Restricted license to drive noncommercial vehicles
	<20/200	No driving license	No specific stand	No driving license
Visual Fields Measured by Goldmann Ill4e or Humphrey 120 points screen.	120° horizontal, 40° vertical or better	No visual field-based objection to an unrestricted driving license provided that the field is about evenly divided around fixation and that no attention- related problems were identified.	Not considered except for monocular patients. For drivers carrying hazardous material, opinion about "side vision" is mentioned but the testing criteria are unspecified.	Unrestricted license
	Worse than 120° horizontal, 40° vertical	Individual consideration, which may include restrictions. Evaluation should include visual and non-visual factors and a road test.		Restricted license to drive noncommercial vehicles
Color Vision Ability to distinguish between pigmentary colors red and green	To be able to identify red and green pigmentary colors	Required to pass	Not required for those <50 years of age. Those >50 years and those for a license to drive transport vehicles, color vision testing by Ishihara chart.	Required to pass for an unrestricted license. Those defective are to be tested with the Ishihara chart. Restricted license to drive noncommercial vehicles for those who read <7 plates.
Glare Recovery Tested by 3- second flashlight test	Ability to read 6 of 7 numbers in a line within 5 seconds of exposure to a flashlight	Not required	Required for drivers carrying hazardous material, but testing conditions unspecified.	Required for drivers carrying hazardous material under specified testing conditions.

*Assessment by an ophthalmologist under standard testing conditions with calibrated equipment. Additionally, patients should be assessed for diplopia and stereopsis if they have a squint or ocular motility restiction. Those with diplopia should not qualify for a driving license. Those with defective stereopsis (>40 seconds of an arc by the Random-dot Stereoacuity Test) or monoculars could qualify for a restricted license. Those with a history of night blindness should be tested by Pelli-Robson Contrast Sensitivity Chart and if deficient, considered for a restricted license.

Restricted license = non-occupational, non-commercial, non-transport personal driving license with or without limitation to daylight driving, restriction to a reasonable radius from home, restriction to familiar areas, speed limitation, no highway driving, and more frequent re-testing.

Visual functions may be one of the most important modifiable factors to ensure better safety and reducing the incidence of RTA. Visual criteria that govern the issue of driving licenses in India do not appear to be objective or assessed under standard testing conditions. The inclusion of appropriate and objective visual function standards may help minimize the incidence of vision-related RTA, an easily avoidable cause of morbidity and mortality. Meeting of minds of the leaders of ophthalmology societies, road safety experts, lawmakers, and the Government authorities, agreement on a set of visual function standards, appropriate modification of the MVA, public education, and strict implementation seem to be the logical steps in the right direction.

“The more precisely I can drive, the more I enjoy myself” – Michael Schumacher