Purpose: To establish age-related, normal limits of monocular and binocular spatial vision under photopic and mesopic conditions. Methods: Photopic and mesopic visual acuity (VA) and contrast thresholds (CTs) were measured with both positive and negative contrast optotypes under binocular and monocular viewing conditions using the Acuity-Plus (AP) test. The experiments were carried out on participants (age range from 10 to 86 years), who met pre-established, normal sight criteria. Mean and ± 2.5σ limits were calculated within each 5-year subgroup. A biologically meaningful model was then fitted to predict mean values and upper and lower threshold limits for VA and CT as a function of age. The best-fit model parameters describe normal aging of spatial vision for each of the 16 experimental conditions investigated. Results: Out of the 382 participants recruited for this study, 285 participants passed the selection criteria for normal aging. Log transforms were applied to ensure approximate normal distributions. Outliers were also removed for each of the 16 stimulus conditions investigated based on the ±2.5σ limit criterion. VA, CTs and the overall variability were found to be age-invariant up to ~50 years in the photopic condition. A lower, age-invariant limit of ~30 years was more appropriate for the mesopic range with a gradual, but accelerating increase in both mean thresholds and intersubject variability above this age. Binocular thresholds were smaller and much less variable when compared to the thresholds measured in either eye. Results with negative contrast optotypes were significantly better than the corresponding results measured with positive contrast (p < 0.004). Conclusions: This project has established the expected age limits of spatial vision for monocular and binocular viewing under photopic and high mesopic lighting with both positive and negative contrast optotypes using a single test, which can be implemented either in the clinic or in an occupational setting.
Purpose: To establish age-related, normal limits of monocular and binocular spatial vision under photopic and mesopic conditions. Methods: Photopic and mesopic visual acuity (VA) and contrast thresholds (CTs) were measured with both positive and negative contrast optotypes under binocular and monocular viewing conditions using the Acuity-Plus (AP) test. The experiments were carried out on participants (age range from 10 to 86 years), who met pre-established, normal sight criteria. Mean and ± 2.5σ limits were calculated within each 5-year subgroup. A biologically meaningful model was then fitted to predict mean values and upper and lower threshold limits for VA and CT as a function of age. The best-fit model parameters describe normal aging of spatial vision for each of the 16 experimental conditions investigated. Results: Out of the 382 participants recruited for this study, 285 participants passed the selection criteria for normal aging. Log transforms were applied to ensure approximate normal distributions. Outliers were also removed for each of the 16 stimulus conditions investigated based on the ±2.5σ limit criterion. VA, CTs and the overall variability were found to be age-invariant up to ~50 years in the photopic condition. A lower, age-invariant limit of ~30 years was more appropriate for the mesopic range with a gradual, but accelerating increase in both mean thresholds and intersubject variability above this age. Binocular thresholds were smaller and much less variable when compared to the thresholds measured in either eye. Results with negative contrast optotypes were significantly better than the corresponding results measured with positive contrast (p < 0.004). Conclusions: This project has established the expected age limits of spatial vision for monocular and binocular viewing under photopic and high mesopic lighting with both positive and negative contrast optotypes using a single test, which can be implemented either in the clinic or in an occupational setting.
One of the most important societal trends affecting our workplace and workforce in the following decade concerns the combination of a smaller number of younger workers relative to their older counterparts, and the current ‘early exit’ culture in Europe. Because of the staff shortages and possible knowledge loss (e.g., Calo 2008; Joe et al. 2013) that may accompany these demographic changes, there is a strong financial reason to retain and sustain ageing employees at work (Kooij et al. 2014; Truxillo and Fraccaroli 2013). In order to respond to today’s labour market needs, many governments have chosen to increase the official retirement age to 66 or even higher. In the Netherlands, for example, retirement age will be gradually raised to 66 years in 2019 and to 67 years in 2023. Other European Union countries have similar plans to steadily raise their retirement ages to 67 years in 2023 (France), 2027 (Spain), or 2031 (Germany). In the UK and Ireland, the retirement age will increase to 68 in 2028 (Ireland) and in 2046 (the UK). However, the reality of older workers’ current employment does not yet match these political ambitions. According to figures collected by the European Union Labour Force in the European Union Labour Force Survey (Eurostat 2014), the EU-28 (i.e., average of the 28 European Union countries) employment rate for persons aged 15–64 was 64.1 per cent in 2013. However, when looking more closely at the country level or when differentiating between age categories, the active labor participation of older European employees does not appear to be as high. The EU employment rate of older workers—calculated by dividing the number of persons in employment and aged 55–64 by the total population of the same age group—was 49.5 per cent in 2013 (OECD 2014), whereas the OECD average was 54.9 per cent in the same year. In the USA and Korea, for example, employment rates of workers of 55–64 years old were, respectively, 60.9 per cent and 64.3 per cent in 2013.
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