Today we will be featuring a guest blog post from our clinical co-ordinator Lisa who will go over the most common terms associated with binocular vision dysfunction.
There is a difference between sight and vision. Sight is the ability to see clearly at any distance. Vision is the ability to process what you see and use it for meaningful purpose.
Sight
Visual acuities measure how well we discriminate detail. 20/20 sight is a term used to express normal visual acuity. Visual acuity is typically measured at a distance of 20 feet. If you have 20/20 sight, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 sight, it means that you must be as close as 20 feet to see what a person with normal sight can see at 100 feet. Having 20/20 sight does not necessarily mean you have perfect vision. 20/20 sight only indicates the sharpness or clarity of vision.Vision
The eyes each have six muscles that control their movement. There are three different cranial nerves, which control these muscles. Movement must be coordinated between these twelve muscles so that the muscles are aligned. Like other muscles in the body, the ocular muscles have a resting position when we are not actively looking at an object. When not aligned properly, the eyes have to make significant corrections to maintain fusion and keep from seeing double.Ocular Motility
These skills involve the ability to aim the eyes, follow a moving object, and track along a line of print accurately. Eye movements require a high level of precision. These skills allow rapid and accurate shifting of the eyes as they track when reading. They also are present when you make quick shifts from distance to near. Ocular motor dysfunction results from an inability to smoothly and accurately control the movement of these ocular muscles under demanding visual conditions. When we read, our eyes make small jumps from one word to the next. When these movements are inaccurate, we may read the wrong word or re-read a word. If this happens several times, information may seem confusing and comprehension is decreased.Accommodation
This skill is the ability to shift the visual focus from far to near objects quickly and accurately and to maintain clarity of objects with a minimal effort. As we age, this ability decreases resulting in the need for reading glasses.Binocular Integration
This skill is related to eye teaming (vergence), eye movement control (ocular motility), and focusing ability (accommodation). Deficiencies in one or a few of these areas can cause symptoms from shadowing or double vision, headaches, or dizziness to name a few. Considerable effort to maintain visual stability is tiring and can result in decreased attention and ability to concentrate.
By evaluating the visual system and specifically the visual skills listed above, it can determined whether you can benefit from a program of vision therapy or rehabilitation. Vision therapy is a joint effort between you, your doctor, therapists, and caregivers all working toward the goal of improving your visual performance.