Comparison of visual requirements and regulations for obtaining a driving license in different European countries and some open questions on their adequacy

Diurnal variation of visual functions for driving with and without orthokeratology: A multicenter study

PURPOSE

To investigate orthokeratology-related diurnal variations in visual acuity, contrast sensitivity, mesopic (twilight) vision, and glare sensitivity, and to verify compliance with requirements for driver licensing.

METHODS

In this prospective, multicenter, controlled study, fifty myopic (range, -1.00 to -4.50 D) and non-presbyopic glasses or soft contact lens wearers (age range, 16-39 years) were fitted with orthokeratology (OK) contact lenses. Before and after completion of OK lens fitting, measurements of visual acuity, contrast sensitivity, mesopic vision and glare sensitivity were performed at three times of the day, morning, afternoon and evening using a standardized binocular vision testing device (Oculus Binoptometer 4P). Monocular and binocular visual acuity were tested according to ISO 8596 and compared to requirements of cars and motorcycles drivers in different countries.

RESULTS

Compared to the prior correction, binocular visual acuity (logMAR) with orthokeratology was statistically significant better in the morning (0.04 ± 0.12; p < 0.05) and afternoon (0.04 ± 0.10; p < 0.05), while the difference was not statistically significant in the evening (p = 0.512). Furthermore, there was no statistically significant difference in contrast sensitivity in the morning (p = 0.813), afternoon (p = 0.742) or evening (p = 0.945). For both mesopic vision and glare sensitivity, there was no statistically significant difference between the contrast levels achieved with orthokeratology compared to the prior correction in the morning (p = 0.083; p = 1.000), afternoon (p = 0.054; p = 0.125) or evening (p = 0.195; p = 0.635). With orthokeratology, no statistically significant diurnal variation was found for binocular visual acuity, contrast sensitivity, mesopic vision or glare sensitivity (p > 0.05).

CONCLUSIONS

These results provide evidence, that visual functions of OK lens wearers are stable throughout the day and comparable to the prior correction. Although the visual standards for driving are not uniform within countries, the requirements for visual acuity are met in all of the countries. Mesopic vision and glare sensitivity, which are suggested as other aspects to influence driving performance, also appear to be constant over the course of the day.

Visual field requirements for driving across various jurisdictions and their rationale

An intact visual field is essential for safe driving and therefore is a requirement for driving in many jurisdictions. There is significant variation in the standards applied. Using an online search, guidelines and policy statements were obtained regarding driving vision standards from jurisdictions who used English as an official language and included visual field requirements. Scientific research cited in these documents was reviewed. The evidence base for vision standards was heterogenous with visual field requirements for the horizontal meridian, the vertical meridian and fixation varying markedly between jurisdictions. Research influencing driving guidelines was unable to provide specific recommendations and relied on different forms of visual field assessment and characterisation. The final visual standards chosen by any one jurisdiction are often of unclear origin. Alternative methods of visual field assessment that better recreates the driving experience may help transport authorities reach a consensus. Additionally more jurisdictions may be able to use visual fields as a barrier to operating a motor vehicle if visual field assessment became more accessible.

Comparison of the Relationship between Visual Acuity and Motor Function in Non-Elderly and Elderly Adults

This study aimed to clarify the relationship between visual acuity and motor function in younger and elderly participants and to compare differences between non-elderly and elderly participants. In total, 295 participants who underwent visual and motor functional examinations were included; participants with visual acuity ≥0.7 were assigned to the normal group (N group) and those with visual acuity ≤0.7 were assigned to the low-visual-acuity group (L group). Motor function was compared between the N and L groups; the analysis was performed by grouping participants into those aged >65 years (elderly) and those aged <65 years (non-elderly). The non-elderly group (average age, 55.6 ± 6.7 years) had 105 and 35 participants in the N and L groups, respectively. Back muscle strength was significantly lower in the L group than in the N group. The elderly group (average age, 71.1 ± 5.1 years) had 102 and 53 participants in the N and L groups, respectively. Gait speed was significantly lower in the L group than in the N group. These results reveal differences in the relationship between vision and motor function in non-elderly and elderly adults and indicate that poor vision is associated with lower back-muscle strength and walking speed in younger and elderly participants, respectively.