More obvious sensory deficits, that the majority of old people encounter, are the declines in vision and audition. Changes in the cornea, lens, and muscles affect vision from the age of 35 (Kline & Schieber, 1985) and changes in the retina and nervous system affect vision from the age of 55 (Keunen et al., 1987). The lens becomes inflexible, leading to problems focusing on near objects (presbyopia), and slowly yellows. The retinal ganglion and receptor cells degenerate, and there is also an increased risk of cataracts, the latter affecting about 25% of 70 year-olds (Corso, 1987).
These changes affect higher level perceptual processing. Visual acuity declines between the ages of 60 and 80 as a smaller pupil and yellower lens reduces the amount of light reaching the retina (Anderson & Palmore, 1974). Impaired depth perception parallels this decline because the older person cannot discriminate detail, and therefore the texture gradient, that is a powerful distance cue. Decreased spatial resolution, temporal resolution, light sensitivity, contrast sensitivity and a smaller visual field are also reported (Fozard, 1990). Older people are slower to process visual information, poorer at tracking moving objects, and have more difficulty extracting particular objects from a complex visual display (Kosnik et al., 1988). Finally the elderly are more susceptible to glare, due to an increasingly opaque lens which scatters light waves as they enter the eye (Carter, 1982).
The reduced visual capability produces poor environmental orientation, decreased mobility, and increased susceptibility to accidents (Hill, 1973). The elderly are 60% more likely to be involved in a road accident than middle-aged people (Planek, 1974), accounting for a quarter of all deaths on the roads (OPCS, 1991a). Although the most important cause of road accidents in the elderly is their slower processing of information, sensory impairments are a significant contributory factor (Planek, 1974). Due to the elderly driver's smaller visual field, they are less aware of cars pulling out of side streets (Jaffe et al., 1986), explaining why older drivers are frequently involved in accidents involving "right of way" violations (Planek, 1974). Old people have problems with dashboard instruments due to difficulty with focusing at near distances (presbyopia), and being slower to change accommodative focus from the instrument panel to the road (Sojourner & Antin, 1990). Night driving is particularly hazardous, since most of the viewing must be done in dim light and, in addition, the lights of oncoming vehicles produce glare (Carter, 1982).
Fortunately the quality of life of the visually-impaired elderly adult can be markedly improved. Cataracts are now operable, the cloudy lens being replaced with a synthetic one and presbyopia can be corrected with spectacles. By the age of 45, 88% of people wear glasses, climbing to 98% by the age of 65 (OPCS, 1991b). Large-print and "talking" books are also available. Large figures should be used for important visual displays, such as traffic signs, clocks, and fire exits, and colour discriminations in the blue-green range (made difficult by the yellow lens) should be avoided (Regnier & Pynoos, 1987). High illumination levels should be used (Kaufman & Haynes, 1981) and buildings should take into account the decreased rate of dark adaptation in the elderly by avoiding sudden shifts in illumination level, especially at places with changes in floor level (Regnier & Pynoos, 1987). Environmental changes can control glare for the elderly, by shielding light sources, using several small low-intensity lights rather than one of high intensity, and using non-reflectant materials on walls, floors and ceilings (Boyce, 1981). Contrast should be optimized at all times, for example, by using white as opposed to grey paper, and ink instead of pencil (Cushman & Crist, 1987).
Turning to audition, 19% of 55 year-olds and 75% of 79 year-olds suffered from some form of hearing loss (Schaie & Geiwitz, 1982). Auditory damage includes sensory presbycusis due to atrophy of the receptor cells, neural presbycusis due to nerve fibre degeneration, mechanical presbycusis due to a decreased elasticity of the basilar membrane and metabolic presbycusis due to atrophy of the stria vascularis. These types of hearing loss preferentially affect high frequency sounds (apart from metabolic presbycusis which affects all frequencies) which are the most important for speech discrimination, and by 80 years-old there is an average decline in speech understanding of 25% (Plomp & Mimpen, 1979). Shouted warnings may be misunderstood or not heard at all, car horns may not be noticed, and ordinary warning sounds, such as breaking glass alerting one to an intruder or screeching brakes, may go unheeded.
Unfortunately, hearing aids are generally a less satisfactory solution to the hearing-impaired adult than spectacles are to the visually-impaired. The best models are expensive, while cheaper ones do not selectively boost high frequencies producing a distracting "booming" effect. There is also a greater stigma associated with wearing a hearing aid, perhaps because presbyopia begins in the thirties, whereas presbycusis does not affect the majority of people until the seventies, and so is taken as indicative of being "over the hill". Supporting this conclusion, while 18% of people over the age of 75 wear hearing aids, a further 25% report severe hearing difficulties yet will not use an aid (OPCS, 1991b). If the elderly individual is to benefit from a hearing aid they must receive considerable encouragement, guidance and instruction and be realistic about the limitations of the instruments, since they do not restore normal hearing. With counselling 60% of elderly hearing aid users can achieve a satisfactory level of social functioning (Jeffers, 1969). The elderly patient should also be taught to lip-read and receive speech training. The latter is required because an individual with presbycusis gradually loses the ability to use auditory feedback to regulate the movements of the articulators (ie. the lips, mouth and tongue).
The acoustic environment can also be altered to maximize the elderly person's remaining auditory abilities. The volume of important sounds should be increased (Regnier & Pynoos, 1987) and warning signals should use low frequency sounds with maximum reverberation, since the physical sensation of vibration may alert the deaf. Background noise can be decreased, for example by avoiding piped music and noisy air conditioning units (Regnier & Pynoos, 1987). Echoes can be reduced by using sound absorbing materials on walls, floors and ceilings (Plomp & Duquesnoy, 1980). Finally, speech should not be too fast since the majority of elderly people cannot follow speech rates faster than 200 words/min.
In conclusion, declining sensory capabilities place the elderly person in a new and restrictive environment. Auditory localisation is less accurate, the defining features of visual objects are blurred, and a once familiar environment becomes confusing, even unrecognisable. Sensory deficits alter a person's social environment affecting their ability to sustain normal interpersonal relations. This can produce feelings of loneliness, insecurity, apathy and indifference. Elderly people with visual and hearing impairments leave their households less often and have fewer social contacts (Birren & Schaie, 1977). Mental competence may decline if the individual begins to avoid interpersonal interactions (Schaie et al.,1964), and emotional lability, paucity of speech and even dementia-like behaviour can result (Maloney, 1987). Some elderly people deny their impairment, while others feel a loss of dignity and identity without adequate environmental contact. This may cause the elderly individual to adopt maladaptive behaviours (Hyams, 1969). For example, deafness is correlated with paranoid psychosis, presumably as the person misinterprets poorly heard conversation as hostile towards them (Cooper et al., 1974). Sensory impairments are also associated with increased risk of depression and decreased self-sufficiency in daily living activities (Carabellese et al., 1993).
Unfortunately the changes discussed in this essay usually occur with other problems, such as infirmities, poverty, widowhood, retirement and an increased dependency on others, thereby straining the individual's personal adjustment. We can alleviate this emotional burden by helping the elderly cope with their sensory impairments. I hope this essay has demonstrated how important, and often how simple it is, to achieve this aim.
References
Anderson, B. & Palmore, E. (1974) Longitudinal evaluation of ocular function. In E.Palmore (Ed.) Normal aging II, Reports from the Duke longitudinal studies, 1970-73, pps. 24-32. Durham, NC: Duke University Press.
Bhala, R.P., O'Donnell, J., & Thoppil, E. (1982) Ptophobia: Phobic fear of falling and its clinical management. Physical Therapy, 62, pps. 187-190.
Bhatnagar, K.P., Kennedy, R.C., Baron, G. & Greenberg, R.A. (1987) Number of mitral cells and the bulb volume in the aging human olfactory bulb: A quantitative morphological study. Anatomical Record, 218, pps. 73-87.
Birren, J.E. & Schaie K.W. (1977) Handbook of the psychology of aging. New York: Van Nostrand Reinhold.
Boyce, P.R. (1981) Human factors in lighting. Essex: Applied Science.
Campbell, A.J., Reinken, J., Allen, B.C., & Martinez, G.S. (1981) Falls in old age: A study of frequency and related clinical factors. Age and Ageing, 10, pps. 264-270.
Carabellese, C., Appollonio, I., Rozzini, R. & Bianchetti, A. (1993) Sensory impairment and quality of life in a community elderly population. Journal of the American Geriatrics Society, 41, pps. 401-407.
Carter, J.H. (1982) The effects of aging upon selected visual functions: Colour vision, glare sensitivity, field of vision and accommodation. In R.Sekuler, D.Kline, & K.Dismukes (Eds.) Aging and human visual function. New York: Alan R. Liss.
Cooper, A.F., Kay, D.W.K., Curry, A.R., Garside, R.F., & Roth, M. (1974) Hearing loss in paranoid and affective psychoses of the elderly. The Lancet, 2, pps. 851-854.
Corso, J.F. (1987) Sensory-perceptual processes and aging. In K.W.Schaie (Ed.) Annual review of gerontology and geriatrics, (Vol. 7), pps. 29-55.
Cushman, W.H. & Crist, B. (1987) Illumination. In G.Salvendy (Ed.) Handbook of human factors, pps. 670-695. New York: Wiley.
Doty, R.L., Shaman, P., Applebaum, S.L., Giberson, R., Siksorski, L., & Rosenberg, L. (1984) Smell identification ability: Changes with age. Science, 226, pps. 1441-1443.
Fox, R.H., MacGibbon, R., Davies, L. & Woodward, P.M. (1983) The problem of the old and the cold. British Medical Journal, 7 pps. 21-24.
Fozard, J.L. (1990) Vision and hearing in aging. In J.E.Birren & K.W.Schaie (Eds.) Handbook of the psychology of ageing (3rd ed.), pps. 50-83. New York: Academic.
Gilbert, A.N. & Wysocki, C.J. (1987) The smell survey results. National Geographic, 170, pps. 324-361.
Hill, D.W. (1973) The management of visual loss. Proceedings of the Royal Society of Medicine, 66, p. 164.
Hinds, J.W. & McNelly, N.A. (1981) Aging in the rat olfactory system: Correlations of changes in the olfactory epithelium and olfactory bulb. Journal of Comparative Neurology, 203, pps. 441-453.
Hyams, D.E. (1969) Psychological factors in rehabilitation of the elderly. Gerontologia Clinica, 11, pps. 129-136.
Jaffe, G.J., Alvarado, J.A. & Juster, R.P. (1986) Age-related changes of the normal visual field. Archives of Ophthalmology, 104, pps. 1021-1025.
Jeffers, J. (1969) The social adequacy of two selected samples of geriatric- presbyacusics with significant hearing losses. International Audiology, 8, pps. 317-324.
Kaufman, J.E. & Haynes, H. (Eds.) (1981) Illumination Engineering Society lighting handbook: Application volume. New York: Illumination Engineering Society of North America.
Keunen, J.E.E., Van Norren, D. & Van Meel, G.J. (1987) Density of foveal cone pigments at older ages. Investigative Ophthalmology and Visual science, 28, pps. 895-991.
Kline, D.W. & Schieber, F. (1985) Vision and aging. In J.E.Birren & K.W.Schaie (Eds.) Handbook of the psychology of aging (2nd ed.). New York: Van Nostrand Reinhold.
Kosnik, W., Winslow, L., Kline, D., Rasinski, K. & Sekuler, R. (1988) Visual changes in daily life throughout adulthood. Journals of Gerontology: Psychological Sciences, 43, pps. 63-70.
Maloney, C.C. (1987) Identifying and treatin the client with sensory loss. Physical and Occupational Therapy in Geriatrics, 5, pps. 31-46.
Ochs, A.L., Newberry, J., Lenhardt, M.L., & Harkins, S.W. (1985) Neural and vestibular aging associated with falls. In J.E.Birren & K.W.Schaie (Eds.) Handbook of the psychology of aging (2nd ed.). New York: Van Nostrand Reinhold.
Office of Population, Census and Statistics (1991a) Mortality statistics by cause: England and Wales. London: HMSO.
Office of Population, Census and Statistics (1991b) General Household Survey. London: HMSO publication.
Ordy, J.M. & Brizzee, K.R. (1975) Advances in behavioural biology (Vol. 16). London: Plenum.
Planek, T.W. (1974) Factors influencing the adaptation of the aging driver to today's traffic. Clinical Medicine, 81, pps. 36-43.
Plomp, R. & Duquesnoy, A.J. (1980) Room acoustics for the aged. Journal of the Acoustical Society of America, 66, pps. 1616-1621.
Plomp, R. & Mimpen, A.M. (1979) Speech-reception threshold for sentences as a function of age and noise level. Journal of the Acoustical Society of America, 66, pps. 1333-1342.
Rango, N. (1985) The social epidemiology of accidental hypothermia among the aged. Gerontologist, 25, pps. 424-430.
Regnier, V. & Pynoos, J. (1987) Housing the aged. New York: Elsevier.
Schaie, K.W., Baltes, P., & Strother, C.R. (1964) A study of auditory sensitivity in advanced age. Journal of Gerontology, 19, pps. 453-457.
Schaie, K.W. & Geiwitz, J. (1982) Adult development and aging. Toronto: Little, Brown.
Schiffman, S.S. & Warwick, Z.S. (1989) Use of flavor-amplified food to improve nutritional status in elderly persons. Annals of the New York Academy of Sciences, 561, pps. 267-276.
Sojourner, R.J. & Antin, J.F. (1990) The effects of a simulated head-up display speedometer on perceptual task performance. Human Factors, 32, pps. 329-339.
Verriollo, R.T., (1980) Age-related changes in the sensitivity to vibration. Journal of Gerontology, 35, pps. 185-193.