Aged Drivers May Experience Decreased Visual Function While Driving

Night Vision and Carotenoids (NVC): A Randomized Placebo Controlled Clinical Trial on Effects of Carotenoid Supplementation on Night Vision in Older Adults

Twilight and low luminance levels are visually challenging environments for the elderly, especially when driving at night. Carotenoid rich diets are known to increase macular pigment optical density (MPOD), which in turn leads to an improvement in visual function. It is not known whether augmenting MPOD can lead to a decrease in vision related night driving difficulties. Additionally, it is unknown if carotenoid supplementation provides additional measurable benefits to one's useful field of view (UFOV) along with a decreased composite crash risk score. The aim of the study was to evaluate changes in night vision function and UFOV in individuals that took carotenoid vitamin supplements for a six-month period compared to a placebo group.

METHODS

A prospective, randomized, double-blind, six-month trial of a 14 mg zeaxanthin/7 mg lutein-based supplement was carried out. Participants were randomized into active or placebo group (approx 2:1).

RESULTS

n = 33 participants (26 males/7 females) participated with 93% capsule intake compliance in the supplemented group (n = 24) and placebo group (n = 9). MPOD (mean/standard error SE) in the active group increased in the Right eye from 0.35 density units (du)/0.04 SE to 0.41 du/0.05 SE; p < 0.001 and in the Left eye from 0.35 du/0.05 SE to 0.37 du, p > 0.05). The supplemented group showed significant improvements in contrast sensitivity with glare in both eyes with improvements in LogMAR scores of 0.147 and 0.149, respectively (p = 0.02 and 0.01, respectively), monocularly tested glare recovery time improved 2.76 and 2.54 s, respectively, (p = 0.008 and p = 0.02), and we also noted a decreased preferred luminance required to complete visual tasks (p = 0.02 and 0.03). Improvements in UFOV scores of divided attention (p < 0.001) and improved composite crash risk score (p = 0.004) were seen in the supplemented group. The placebo group remained unchanged.

CONCLUSIONS

The NVC demonstrates that augmenting MPOD in individuals with difficulty in night vision showed measurable benefits in numerous visual functions that are important for night vision driving in this small sample RCT. Additionally, we observed an improvement in UFOV divided attention test scores and decreased composite risk scores.

Machine-learning approach to predict on-road driving ability in healthy older people

AIM

In Japan, fatal traffic accidents due to older drivers are on the rise. Considering that approximately half the older drivers who have caused fatal accidents are cognitively normal healthy people, it has been required to detect older drivers who are cognitively normal but at high risk of having fatal traffic accidents. However, a standardized method for assessing the driving ability of older drivers has not yet been established. We thus aimed to identify a new sensing method for the evaluation of the on-road driving ability of healthy older people on the basis of vehicle behaviors.

METHODS

We enrolled 33 healthy older individuals aged over 65 years and utilized a machine-learning approach to dissociate unsafe drivers from safe drivers based on cognitive assessments and a functional visual acuity test.

RESULTS

The linear support vector machine classifier successfully dissociated unsafe drivers from safe drivers with accuracy of 84.8% (sensitivity of 66.7% and specificity of 95.2%). Five clinical parameters, namely age, the first trial of the Rey Auditory Verbal Learning Test immediate recall, the delayed recall of the Rey-Osterrieth Complex Figure Test, the result of the free-drawn Clock Drawing Test, and maximal visual acuity, were consistently selected as essential features for the best classification model.

CONCLUSION

Our findings improve our understanding of clinical risk factors leading to unsafe driving and may provide insight into a new intervention that prevents fatal traffic accidents caused by healthy older people.

Shortened Measurement Time of Functional Visual Acuity for Screening Visual Function

The functional visual acuity test which is the average of the visual acuities measured during a specific time frame (standard, 60 seconds) has been used recently to assess the visual function in various conditions. The availability of a shorter version of the functional visual acuity test promises to be patient friendly in that it is a simple screening test performed in a shorter period of time than the standard test. The results of measurements of the FVA test between the 30-second measurement time (short-version FVA test) and the standard 60-second measurement are compared, and the feasibility of the short-version FVA test instead of the standard FVA test is investigated. Twenty-eight healthy volunteers (25 men and 3 women) were enrolled in this prospective observational study. All subjects underwent measurement of the binocular distance-corrected visual acuity and the binocular distance-corrected FVA with the 60-second and 30-second measurement times. The interchangeability of the corrected-distance FVA, maximal VA, visual maintenance ratio, and average response time in the short-version and the standard FVA tests was evaluated using the Bland–Altman method, and the results showed agreements of the two tests except for the minimal VA. The short-version FVA test is equivalent to the standard method except for evaluating the visual acuity fluctuations and promises to be a simple visual screening test that can be performed in a shorter time.

Functional Visual Acuity

Dry eye (DE) causes irregularity of the ocular surface and reduces the quality of vision. An intact, regular tear film is essential for high-quality retinal images; however, visual tasks requiring sustained gazing can disrupt the tear film, eventually degrading visual function. A functional visual acuity (FVA) measurement system has been uniquely developed in Japan to evaluate visual function related to tear stability in patients with DE. FVA has been shown to correlate with optical quality. The system measures the change in visual acuity (VA) over time automatically in aqueous-deficient DE and short tear breakup tear film DE characterized by decreased tear stability and minimal epithelial damage. It is also useful to detect minimal visual deterioration correlated with minimal ocular surface abnormality and vision-related quality of life otherwise undetectable by conventional VA testing, to assess and quantify vision-related symptomatology, and to determine the efficacy of treatments for DE disease. Recently, its use has been expanded, such as for the analysis of visual function accompanying refractive surgery, contact lens, cataract and cataract-related disease, retinal disease, glaucoma, amblyopia, presbyopia, and vehicle driving. Its use has revealed that FVA reflects not only visual function related to tear dynamics, but also visual function related to quick recognition of the target. This simple, noninvasive, and sensitive FVA measurement system may be expected to be used worldwide.