The term functional vision stands for vision that person uses for planning and performing daily tasks. That vision is exceptionaly important for persons who have small percentage of vision (less than 10%), because, in previous years, when the grades of blindness and low vision weren't well known, it was considered that persons with such a small amount of vision can't see at all and were considered blind. Also it was considered that every percentage of vision , that person has, should be saved, instead of being used and, in that way, wasted. After the importance of every remaining vision was perceived, the belief which considered the vision protection, ended, and the accent was on encouaring people to use their vision and then the program of vision exercises was developed- it encouraged its use and development of its functionality. When using functional vision, it is necessary to make certain adjustments that are very useful for visually impaired people in everyday activities, and to be sure that they are relevant, it is very important to make both functional vision and visual function assessment. It is important to mention that visual functions tell us how eye and the visual system function. The aim of this research project is to show that amount of person's vision doesn't determine how well the person will function visually, but the way of using the remaining vision in different activities of daily living is a real indicator of how much a person actually sees. With this research I want to show that besides the visual functions, there are other factors affecting person's visual functioning, such as illumination, saturation of visual surface, contrasting, etc. The students participating in this research attended „Vinko Bek“ high school (n=5) and were between 15 and 20 years old. This research will show that visual function assessment musn't be neglected, nor the adaptation of the environment in accordance with it.