VISUAL CONSIDERATIONS
Visual considerations should be given prior importance while designing an automobile as it has direct effects on its design and design is supposed to be a very crucial factor as undoubtedly it is the thing that decides whether people are going to like it and buy it or not.
With increase in age, there is gradual loss of elasticity in almost all the muscles of the body including muscles of eyes. This reduction in elasticity of the eye muscles lead to inability of the person to focus on an object kept at a distance. This condition gets worse in the situation of dim light or excess light. Along with decreased muscle elasticity, the lens of the eye also become less transparent with increasing age as there is alteration in the chemical composition of the lens (Haigh, 1993). This further poses difficulty in focussing on an object. The ability to focus on a distant object is also affected and reduced by the decrease in elastic property of eye muscles controlling the shape of the lens or the muscles that aid in contraction of lens. Therefore the efficiency of eyes is greatly reduced with increasing age.
Ageing also causes changes in the near point of a person. More light is required with increasing age for improved contrast. Nearly double illumination is required for 40 years old people and triple for 60 years old when compared to the young people of about 20 years (Haigh, 1993). The problem of temporary vision impairment caused due to the bright light (glare) also increases with age only. The capability to prevent glare is usually reduced to half in 12 years. (Reuben et al., 1988).
Visual Fields
1. About one in seven over 65 has abnormal visual fields (Johnson and Keltner, 1983).
2. Thirteen percent over 65 exhibit a field deficit; 3.5% had severe loss of visual fields
3. 57.6% of those with abnormal vision were previously unaware of this