Section 12


Immediate contraindications to driving — a patient with any of the following problems should be advised not to drive until the condition has been evaluated and treated:

  • Visual acuity: For non-commercial drivers, corrected vision worse than 20/50 (6/15) with both eyes open and examined together; for commercial drivers, refer to visual acuity standards in the particular jurisdiction.
  • Visual field: For non-commercial drivers, field less than 120°* along the horizontal meridian and 15° continuous above and below fixation, with both eyes open and examined together; for commercial drivers, refer to visual field standards in the particular jurisdiction.
  • Diplopia within the central 40° of the visual field (i.e., 20° to the left, right, above, and below fixation).
  • Recent functional change from binocular to monocular vision, including temporary patching of an eye.

*The province of Quebec has different requirements for non-commercial drivers (e.g., field less than 100° along the horizontal meridian and 10° continuous above and 20° below fixation, with at least 30° on each side of the vertical meridian, with both eyes open and examined together).

12.1 Overview

The following recommendations are based in large part on the work of the Canadian Ophthalmological Society’s expert working group on driving and vision standards.

When a patient is visually impaired, the physician should inform the patient of the nature and extent of the visual defect and, if required, report the problem to the appropriate authorities.

When minor visual defects are not accompanied by cognitive defects or neglect, most drivers are capable of compensating for the defects. For example, most people adapt to the loss of an eye within a period of several months. Recent studies indicate that experienced drivers can compensate for a loss of visual acuity if they are in familiar surroundings and they limit their speed (Patterson et al., 2019). In these circumstances, functional assessments are indicated.

This section begins by presenting information about the recommended visual acuity and visual field needed for safe driving. Actual standards for these functions are set by provincial or territorial licensing authorities and may vary among jurisdictions, as well as differing from the recommendations in this section, which are based on expert opinion. The section also presents information about other important visual functions that should be taken into consideration in determining fitness to drive and recommendations for exceptional cases that require individual assessment. It also provides a list of medical conditions with increased risk for vision problems and a discussion of the use of vision aids in driving.

12.2 Recommended visual functions

12.2.1 Visual acuity (corrected)

Drivers’ visual acuity must allow them time to detect and react to obstacles, pedestrians, other vehicles, and signs while moving at the maximum posted speed, both in daylight and in darkness. Greater levels of visual acuity are required for some classes of licence to ensure public safety. Road signs should be designed to be easily legible at a safe distance for all individuals who meet the minimum visual acuity standard.

Class of licenceRecommended visual acuity
Non-commercial (Classes 5, 6)Not worse than 20/50 (6/15) with both eyes open and examined together.
Commercial (Classes 1–4)Not worse than 20/30 (6/9) with both eyes open and examined together. Worse eye not worse than 20/400 (6/120).*
*Some jurisdictions require an acuity better than 20/400 (6/120) in the worse eye. For example, some jurisdictions have a standard of 20/100 (6/30) or better in the worse eye for commercial licences. Other jurisdictions, such as Quebec, no longer have requirements for the worse eye.

12.2.2 Visual field

An adequate continuous visual field is important to safe driving. Any significant scotoma or restriction in the binocular visual field can make driving dangerous. Conditions often associated with loss of visual field are described in Section 12.5, Medical conditions and vision aids for driving. If a visual field defect is suspected (on the basis of a medical condition, subjective report, or confrontation field assessment), the patient should be referred to an ophthalmologist or optometrist for further testing.

Class of licenceRecommended visual field
Non-commercial (Classes 5, 6)120° continuous along the horizontal meridian and 15° continuous above and below fixation with both eyes open and examined together.
Commercial (Classes 1–4)150° continuous along the horizontal meridian and 20° continuous above and below fixation with both eyes open and examined together.

12.2.3 Diplopia

Diplopia (double vision) within the central 40° (i.e., 20° to the left, right, above, and below fixation) of primary gaze is incompatible with safe driving for all classes of licence. Individuals who have uncorrected diplopia within the central 40° of primary gaze should be referred to an ophthalmologist or optometrist for further assessment. If the diplopia can be completely corrected with a patch or prisms to meet the appropriate standards for visual acuity and visual field, the individual may be eligible to drive. Before resuming driving with a patch, there should be an adjustment period of 3 months or a period sufficient to satisfy the treating ophthalmologist, optometrist, or occupational therapist that adequate adjustment for driving has occurred. The treating specialist should be experienced in driving assessment.

12.3 Other important visual functions for driving

12.3.1 Colour vision

Individuals should be made aware of any abnormality of colour vision to allow them to compensate for this difference in their vision. Although no formal testing standards exist for colour vision, all drivers should be able to discriminate among traffic lights.

12.3.2 Contrast sensitivity

Loss of contrast sensitivity can be associated with increased age, cataract, refractive surgery, and other ocular disorders. Individuals should be made aware of any significant reduction in contrast sensitivity. Individuals with reduced contrast sensitivity may experience difficulty with driving, especially at night or during bad weather, in spite of meeting visual acuity requirements. There are no quantitative minimum requirements for contrast sensitivity; however, drivers are required to be able to discriminate among traffic lights of different colours.

12.3.3 Depth perception

Motor vehicle crashes sometimes occur because of the driver’s inability to judge distances accurately. Monocular judgments of depth can be made on the basis of such cues as the relative size or interposition of objects, clearness of details, and analysis of shadows and contrast effects. A more refined form of distance judgment, called stereopsis, is based on information coming from both eyes.

Judging distance is a skill that can be learned, even by people with monocular vision, who would fail standard tests for stereopsis. A driver who has recently lost sight in an eye or has lost the use of stereopsis may require a few months to recover the ability to judge distance accurately.

12.3.4 Dark adaptation and glare recovery

The ability to adapt to decreased illumination and to recover rapidly from exposure to glaring headlights is of great importance for night driving.

The partial loss of these functions in elderly people, particularly those with cataracts or macular disease, may in some cases justify limiting driving to daylight hours.

12.3.5 Useful field of view

Processing of visual information while driving is very complex, and the visual field test evaluates only the capacity of a non-moving eye to see a stimulus. The useful field of view test is a specialized visual field test that evaluates the processing speed of centrally presented stimuli, as well as the selective and divided attention a driver needs to identify central and peripheral stimuli presented simultaneously, while ignoring distracting stimuli. Although it is not part of the current regulations, physicians must be aware of this tool and of the importance and complexity of visual information processing for safe driving.

12.3.6 Monocularity

The definition of monocularity varies within the literature, ranging from either complete loss of vision in one eye or impairment of vision below a specific cut-off (such that the second eye is functionally noncontributory) to binocular summation. For the purposes of this guide, monocularity is defined as visual acuity of 20/200 or worse and/or a visual field of 20° or narrower in one eye (legal blindness), or removal of one eye. Patients who are newly monocular should have a full ophthalmological examination, including acuity and visual field testing, before they return to driving. The literature suggests that 50% of patients will adjust to monocularity for many daily tasks within 1 month and 93% will have adjusted by 1 year (Linberg et al., 1988; McLean, 2011). A repeat examination should be scheduled for 3 months from the initial baseline exam and a follow-up consultation (with ancillary testing if needed) for 1 year from the baseline exam. Newly monocular patients may return to driving once their treating ophthalmologist has completed baseline (and any additional) screening as outlined above and is satisfied that they have adapted well to their monocular status. Individuals who are monocular from the beginning of their driver training (e.g., were monocular as children), as well as those who have had a slow loss of vision in one eye, are able to drive, provided they meet the criteria outlined elsewhere in this guide.

12.4 Exceptional cases

The loss of some visual functions can be compensated for adequately, particularly in cases of longstanding or congenital impairments. When a driver becomes visually impaired, the capacity to drive safely varies with the driver’s compensatory abilities. As a result, there may be individuals with visual deficits who do not meet the vision standards for driving but who are able to drive safely. Conversely, there may be individuals with milder deficits who do meet the vision standards but who cannot drive safely.

In these exceptional situations, it is recommended that the individual undergo a special assessment of fitness to drive. The decision regarding fitness to drive can only be made by the appropriate licensing authorities. However, examining physicians may take the following information into consideration when making recommendations to a patient or to the licensing authorities:

  • favourable reports from the ophthalmologist or optometrist
  • good driving record
  • stability of the condition
  • absence of other significant medical contraindications
  • other references (e.g., professional, employment)
  • assessment by a specialist at a recognized rehabilitation or occupational therapy centre for driver training.

In some cases, it may be reasonable to recommend that an individual be granted a restricted or conditional licence to ensure safe driving. It may also be appropriate to make such permits exclusive to a single class of vehicles.

12.5 Medical conditions and vision aids for driving

Some medical conditions have a greater risk of associated vision problems. Examples include the following:

  • Corneal scarring
  • Eye movement disorders
  • Refractive surgery
  • Strabismus
  • Cataract
  • Stroke
  • Diabetic eye disease
  • Brain tumour and surgery
  • Retinal disease
  • Head trauma
  • Optic nerve disorders
  • Neurologic disorders
  • Glaucoma
  • Multiple sclerosis

There are many other conditions that may cause vision problems. If a vision problem is suspected as a result of a medical condition, it is recommended that the individual be referred to an ophthalmologist or optometrist for further assessment of visual function.

Night driving: When assessing a driver’s ability to drive at night, the following factors should be considered: mesopic visual acuity, glare sensitivity, contrast sensitivity, and the presence of pathology such as cataracts, retinitis pigmentosa, corneal scarring, and retinal diseases.

Vision aids and driving: Telescopic spectacles (bioptic devices), hemianopia aids, and other low-vision aids may enhance visual function. The problems associated with their use while driving can include loss of visual field, magnification causing apparent motion, and the illusion of nearness. Although expert opinion does not support their use by low-vision drivers, recent Canadian legal decisions, such as British Columbia (Superintendent of Motor Vehicles) v. British Columbia (Council of Human Rights), oblige licensing authorities to evaluate their use on an individual basis for drivers whose vision does not meet the established standards.

These aids cannot be used to enable the user to meet the visual standards for testing by the licensing authority. Consequently, drivers must demonstrate that the use of the low-vision aid permits them to drive safely despite failure to meet the established visual standard. An on-road test is the usual means of functional assessment in these cases. It should be noted that drivers using telescopic lenses look through the lenses only 5%–10% of the time that they are driving. Consequently, some jurisdictions assess the driver without the lenses to evaluate fitness to drive under the conditions that will prevail for 90% of the time behind the wheel. If the licence is obtained using a vision aid, then the driver must always use the vision aid while driving.

Acknowledgement: Additional contributions to the section were provided by Dr. Jon Waisberg.


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