With the ever increasing number of vehicles using our roads, it is inevitable that drivers need to call upon increasing use of sensory and motor skills in order to negotiate safely through the traffic. Approximately 95% of the sensory input to the brain required for driving comes from vision. So it is obviously essential for adequate standards of vision to be set for the driver of any vehicle and these are set down as either statutory requirements or guidance from the professional body i.e. The College of Ophthalmologists of Sri Lanka
Initial and renewal applicants are required to take and pass a vision test before being issued a license.
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Commercial vehicles |
Non commercial vehicles |
Visual acuity
In examining Snellens test type and the standard near vision testing should be used.
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6/9, 6/12 or vice versa with or without glasses
Should wear corrective lenses ( Spectacles/ contacts) when driving.
The appropriate correction needs to be tolerated by the driver. |
6/9, 6/12 or vice versa with or without glasses
Should wear corrective lenses ( Spectacles/ contacts) when driving.
The appropriate correction needs to be tolerated by the driver. |
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Field of vision
Test should be carried out binocular Esterman visual fields (white target size Goldman iii4 e) |
140 º in the horizontal meridian
No defect within 20 º from fixation horizontally or vertically |
140 º in the horizontal meridian
Defect in one eye should be completely compensated by the other eye |
Monocular vision |
Absolute contraindication |
Monocular vision under special circumstances on an individual basis could be considered provided that following criteria are met
Visual acuity is 6/9 or better with or without correction. Uncorrected minimum vision should be 6/36
visual fields – 120 º in the horizontal meridian
No extension of peripheral defect within 20 º from fixation horizontally or vertically
Within central 20º single missed point or cluster of 3 adjoining points is acceptable if there are no other field defects |
Colour blindness |
No restriction |
No restriction |
Diplopia |
Absolute contraindication |
Assess on an individual basis. Diplopia in the primary position presents an extreme hazard to safe driving. Cessation of driving until the diplopia is controlled with patching or glasses with prisms. Can allow as long as criteria for vision and visual fields are met after a period of 6 months if there is satisfactory functional adaptation. |
Progressive disorders affecting vision / visual field or night vision |
Absolute contraindication |
Can allow as long as criteria for vision and visual fields are met. Review every 2 years for renewal of the license. |
Nystagmus |
Absolute contraindication |
Can allow as long as criteria for vision and visual fields are met. |
Blepharospams |
Absolute contraindication |
Consider on an individual basis. Can allow grade one and two as long as criteria for vision and visual fields are met. |
Squint |
Absolute contraindication as this can impair binocular single vision |
Assess on an individual basis. If an alternative squint with adequate visual acuity and visual fields can be allowed. Squint with diplopia, consider criteria for diplopia. |
Notes on visual fields
The minimum visual field for safe driving is a field of vision of at least 120o on the horizontal meridian measured by the Goldmann perimeter on the III4e settings (or equivalent perimetry). In addition there should be not more than a cluster of 3 non seeing spots in the binocular field which encroaches within the central 20o of fixation. By this means, homonymous or bitemporal defects which come within 20o of fixation, whether hemianopic or quadrantanopic, are not accepted as safe for driving. Isolated scotomata represented in the binocular field near to the central fixation area are also inconsistent with safe driving.
The test must therefore monitor the central area of field as well as its outer perimeter and the intervening meridians. It is obviously essential that the application of the standard should not be equipment specific and the phrase "equivalent perimetry" allows the development of equivalent programs using other perimeters including autoperimeters. Suprathreshold screening tests which cover the central and peripheral field in each eye are commonly available on most autoperimeters and will satisfy the standard. Central threshold tests, commonly used for routine monitoring of glaucoma, are helpful in assessing the significance of a scotoma in the central field but in isolation are not useful.
Where the driver has obvious field defects such as a homonymous hemianopia or quadrantanopia then no confusion arises and the licence is refused. This applies even when the patient has, for whatever reason, been driving with this condition for many years. The problem arises, however, when there are equivocal field losses that only just encroach into the permitted field for driving. These may not necessarily be repeatable especially in the elderly who can have problems mastering the perimeter, or in patients with early glaucoma or lightly photocoagulated diabetics. To be fair to these patients, it is important to test them on more than one occasion to enable an appropriate decision to be made regarding their driving ability. The Esterman binocular field test allows some enhancement of the binocular field as occurs naturally and also allows fixation by the dominant eye. Hence it can be seen to be the least stringent test fulfilling the required standard. It may therefore be used to the benefit of the patient. However, it must be stated that if the Esterman test is failed, even by one spot within the 20o limit, it is likely that this represents a significant scotoma which will lead to the loss of the driving licence. The score given by the program is weighted to the areas of field important to driving but is of little help in the assessment of the standard. Severe bitemporal hemianopia which extends to the midline on either side can still give a horizontal binocular field of 120o on an Esterman or other binocular field by way of binasal vision. It is felt that despite this "full" field, driving is unsafe due to the instability of the two hemifields and the inability of the driver to "lock" the fields from the two eyes together.
Some patients produce very different field test results at different times and it is important to maximise reliability and reproducibility of the visual field test in all cases. False negative and positive errors as well as fixation losses must be minimised to produce accurate results. A field should be rejected if there are more than 20% of false positive errors. A perimetrist should be present with the patient at all times during the test and should carefully explain the test to the patient prior to beginning. Spectacles, especially for a high ametrope, may produce aberrations and a more accurate test may be produced without them.
Notes on monocular vision
Monocular vision is not a cause for disqualification for non commercial vehicles, providing the visual field in the remaining eye is within the above definition. This physiological blind spot may be picked up on an Esterman test in a monocular patient and if this is the case, other central visual field tests such as the Humphrey 24-2 threshold tests should be supplied to demonstrate the otherwise normality of the central field.
For drivers with monocular vision following modifications to the vehicle should be considered. Modified vehicle must present at the time of examination.
- Disable symbol should be displayed
- Only specified motor vehicle
- 2 rear mirrors and 2 front mirrors
- Speed has to be decided by the DMT
- After making modifications to the vehicle need to allow at least 6 months adaptation time from the time of loss of vision on one side or as decided by the consultant ophthalmologist.
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