Vision development occurs most rapidly during the first years of life. Later development slows down and lasts until puberty. As the organism ages, there is a change in the organs, including those related to vision. During healthy aging, certain functions in visual functioning decline, and thus this affects one’s participation in activities of daily life. One of the important parameters in the assessment of visual functions, which is increasingly discussed in the development of neuroscience and physiology of the visual system, is contrast sensitivity. Although it is said that the visual function of contrast sensitivity decreases with age, previous research results have given contradictory results; some state that there is no change or that they are characteristic of certain spatial frequencies. In addition, only the results of research comparing middle-aged people with children and older people are available, so the intention of this research is to gain insight into possible differences in the visual function of contrast sensitivity between preschool children and older people since are involved in different activities of daily living. Respondents in the first group will be preschool children, and in the second group are eldery people. For the purpose of the research, the Mars Perceptix Numeral test was used during the assessment, which is standardized and can be performed monocularly, but the test was conducted binocularly so that we could get information about the activities of everyday life. In addition, the aim of testing this function is to compare the difference with the hypothesis that the elderly will have significantly lower scores than preschool children. 50 respondents in the first group were aged between 5 and 6 years and attended Slavuj kindergarten and 41 respondents in the second group of people over 65 were tested, of which 20 are users of the Sveta Ana Retirement Home, and 20 of them live independently. The results showed that the contrast sensitivity function in childhood was developed in accordance with the norms of this test, while the results of the group of elderly people indicate a weakening of this function, not only in relation to preschoolers, but also in relation to the norms obtained by the test and in that way indicate the importance of continuous assessment of the visual function of contrast sensitivity, which is crucial in performing everyday life activities and can contribute to increasing the quality of life of users. It also provides a good basis for future research to determine at what age a rapid decline in this function occurs and accordingly make the necessary adjustments for successful functioning.