"Line of vision" is a phrase commonly used to describe the path of an observer's sight. However, there are numerous synonyms that can be used interchangeably with this phrase. One common synonym is "line of sight," which has a similar meaning. Another option is "field of view," which refers to the area that can be seen from a specific vantage point. Additionally, "perspective" and "viewpoint" can be used to describe the way in which someone sees something. These synonyms provide a variety of alternatives to the phrase "line of vision" and can help add variety and clarity to written or spoken content.