Visual standards in commercial driving.

Objectives: The study was carried out to review the ocular factors involved in road traffic accidents (RTA) in order to reduce associated injuries and possibly suggest a standard for driving.

Materials And Methods: The study was carried out in the eye clinic of Ladoke Akintola University of Technology Teaching Hospital, Osogbo between May and June 2004. A stratified random sample technique was used to select 99 drivers (198 eyes) from 6 motor park units. Information obtained included age, sex, past history of road traffic accident (RTA), visual acuity and field, colour vision and ability to read number plate tests.

Results: Six drivers (6.1%) were visually impaired. There were 5 cases of monocular blindness. Twenty (20.20%) drivers had accidents in the past, 24(24.24%) could not read number plate at 20.5meters, 6 (6.1%) were colour blind while 36 had visual field loss within 120 degrees horizontally. All the six drivers that had visual field loss encroaching within 20 degrees of fixation had accidents in the past.

Conclusion: This study has shown that there is need to improve on the standard of vision testing before licenses are issued or renewed. Where visual acuity alone is used, it must be done properly by testing one eye at a time. However, a comprehensive eye test using a battery of tests comprising visual acuity, colour vision, visual field and number plate test at 20.5 meters before first issue of driving license and at renewals will be better. Drivers with visual impairment or inability to read number plate test at 20.5 meters should be disqualified from driving commercial vehicles. Drivers with monocular blindness or visual field loss encroaching within 20 degrees of fixation must also not be allowed to drive commercial vehicles. However, further large scale studies will be necessary in order to prove all these propositions scientifically.