Common Misconceptions about Vision
There are two terms that are interchanged often with the assumption that they have the same meaning, sight and vision. Although those terms may appear to mean the same, they have very different meanings.
Sight is how well an object is seen. It often is measured using the familiar Snellen Chart (i.e. 20/20, 20/40, etc). The higher the second number on the Snellen chart, the blurrier your vision is; meaning 20/80 vision is worse than 20/20 vision. Sight is definitely important, however, it's only one of many skills that are used in vision. Aside from eye health, sight is often the only area that gets attention at an eye exam.
Often the allied health professionals that we collaborate with suggest to their patient seeks a functional vision assessment, usually the response is “I just had an eye exam”, I don't need another one. Yes...but, more than likely sight was the only major item assessed.
Vision encompasses so much more; vision is how meaning is derived from sight. Vision is how meaning is derived from the world around us.You have to be able to see (sight) the world first, then
from that information, you can apply meaning and intrepretation. Keep in mind though, just because you can see something, doesn’t necessarily mean you understand it or that you can draw meaning from it. Vision is that process of drawing meaning. It is also a learned skill; meaning that vision is not something a person is born with. Vision is learned by experience. When an infant is creeping and crawling around the floor of a room, they are gaining an understanding of textures, objects and how those objects and textures feel. They gain this understanding usually by first putting the object in their mouth. As their experiences grow, they don’t have to put objects in their mouth or feel them with their hands to understand what the object is. They can “feel” the objects with their eyes (vision). They understand through past experiences what that object means. Just think about how much more efficient it is to see something and understand it, and how extremely inefficient it would be if you had to touch everything in order to understand.
This is also true with time and space. When an infant sees an object across the room, they crawl over to it. Depending on how long it takes them to get to that particular object, they gain an understanding of time and space. They also understand where objects are in their spatial world relative to them (i.e. closer to, farther than). They then further gain understanding of space by utilizing specific visual skills like convergence (point eyes towards nose) and divergence (point eyes away from nose). The infant/toddler gains an understanding of an object that is coming towards them (convergence) or moving away from them (divergence). Convergence and divergence are important vision skills. Accommodation (eye focusing) is another important learned visual skill. The lens inside your eye actually changes shape to bring objects into focus. The amount of focusing (accommodation) that is applied is dependent on the distance of the object. When an object comes near, the eye must focus, or accommodate to keep the image clear.
The goal is to help you understand that although sight is important it doesn't convey the whole picture. Just because vision is 20/20, does not mean there couldn't be a potential underlying vision issue. Hidden vision issues are more common than one would anticipate. They can also be difficult to identify if not assessed by a trained professional. The good news is underlying vision delays can be identified and can be remedied by proper vision therapy.