Visual perception testing is a favorite of therapists. It offers standardized results. It also builds a construct of vision that is utilized to make questionable inferences about observed functional difficulties. Read more about this.
Visual Processing is so much more
The processing of the visual signal begins in the retina with the sharpening of images and the processing of color information. Once in the brain, visual information influences posture and balance. This visual input is also used to develop a spatial map that allows us to safety move through the environment.
A visual journey in the woods
Its sunny day so you decide a brisk hike in the woods. As you walk down the the trail, your central visual system spots the trail as you walk and helps you stay on the trail. Your peripheral visual system maps the space around you.
Just off the trail there is a movement which triggers a quick saccade to investigate this change. The change in the spatial map (the movement) targets your eye to the movement (shifting from peripheral to central input). You briefly stop and see a squirrel that quickly runs as he sees you. The accuracy of this saccade to spot the squirrel was dependent on the spatial map developed by your magnocellular visual tract.
Ahead on the trail you notice a tree branch across the trail and a hill. You continue walking without difficulty, stepping over the branch without looking down. Your spatial map was accurate and you did not trip over the branch. As you begin the hike up the hill, you notice different muscles beginning to work as your posture adjusts for you to climb the hill. Your magnocellular system perceives the change in the ground and adjusts your posture. This successful navigation was all the result of visual information being appropriately processed.
Visual Processing is not so narrow
As therapists, we observe behaviors and make inferences as to the cause of these behaviors, then develop a plan of care to alter the behavior. Visual spatial processing plans a big role in many of the behaviors we observe.
- a clumsy reach-the visual system helps guide reach
- poor eye-hand coordination-spatial mapping allows for accurate targeting during reach
- difficulties with personal space-spatial mapping also maps near and far
- skipping lines or words during reading-accurate saccades require an accurate spatial map and good peripheral awareness
- difficulties in balance-peripheral awareness influences balance
Recognizing these behaviors as a function of the visual system highlights the need for a complete eye exam for every child. Only accurately visual information with the best acuity and best possible eye teaming yields accurate visual processing.