Assessment of visual function amongst motor vehicle drivers in Maseru, Lesotho.

Abstract

Background: Driving is a primary mode of travel in many countries. It relies primarily on the function of vision to navigate roads and traffic safely. Ensuring good vision for motor vehicle drivers is therefore important to promote safety for all road users. Lesotho is a developing country, with road transportation central to the movement of people and goods within, and across the borders of the country. The absence of clear minimal requirements for visual function among holders of motor vehicle licences in Lesotho motivated this study. Aim: To assess the visual function of motor vehicle drivers in Maseru, Lesotho. Methods: A descriptive, mixed methods cross-sectional study employing systematic random sampling was conducted at the Traffic Department in Maseru, Lesotho. Active licensed drivers, both males and females, from 22–76 years of age participated in the study. Data was collected by means of key informant interviews, structured questionnaires and a comprehensive vision examination of all participants. Quantitative data was analysed using Strata version 14 software, while qualitative data was analysed descriptively. Results: The study included 460 licensed drivers with an overall mean age of 42.9 years, of which 64% (n=294) were men. One in five participants had not had an eye examination before obtaining their driving licence. Most participants (70.87%) had normal vision (6/9 or better) in the better-seeing eye, while 29.13% had visual acuity worse than 6/9 in the better-seeing eye. Among those with sub-normal vision, 29% had visual acuity ranging between 6/18 and 6/48 in the better-seeing eye. More than one third (39%) of participants had some form of refractive error, with myopia showing the highest distribution (46.46%), followed by astigmatism (32.96%) and hyperopia (24.59%). Of those with hyperopia, the majority (98%) were classified as having mild hyperopia (+0.50DS up to +2.00DS). Although myopia had the highest distribution, most cases were mild to moderate myopia (-0.50DS up to -5.75DS). The majority of participants (97.61%) passed the colour vision test, 53.70% achieved contrast sensitivity of up to 6/12 in the better eye and 99.6% achieved a measurement of 100 degrees for visual field test screening. Most participants did not wear spectacles when driving, with 37% of these having previously been advised to wear them based on identified need. Almost half (44%) of the participants reported to have been involved in road traffic accidents.

Discussion: While most participants in this study presented with good vision for driving, it is concerning, that almost one in three (29%) had mild to moderate visual impairment and 39% had refractive error, yet they continued to drive without any form of refractive correction. Also, almost half of the participants (44%) had been involved in road traffic accidents, with almost one in five (19%) who had refractive error. It is possible that refractive error and visual impairment could have contributed to their involvement in road traffic accidents. The visual function findings in this study suggest that the Traffic Department in Lesotho should have guidelines on the minimum visual requirements for driving, as well as routine screening procedures. Conclusion: A significant proportion of the motor vehicle drivers in Lesotho have some form of compromised visual function, with many not undergoing an eye examination before obtaining a driver’s licence. If drivers are advised to have their eyes examined regularly, many visual function anomalies could be detected early and their vision corrected accordingly. The absence of effective screening methods for drivers in Lesotho could possibly be a contributor to the incidence of road traffic accidents in the country with the resultant negative socio-economic impacts.