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Functional Vision

Learning requires efficient visual function. Eye movements, focusing (accommodation) and ocular alignment at different distances (vergence) are visual skills necessary for success in the classroom. These three aspects of visual function, if not working efficiently, can affect a child’s visual information processing and ability to learn. If there is too much effort required for clear and single vision, then concentration and comprehension can suffer.

Eye Movement Disorders

The two types of eye movements we test are pursuits and saccades. Although not required for reading, testing pursuit movements is essential. Any dysfunction of pursuit movements indicates a possible generalized ocular motor deficit. Also because pursuit movements require conscious effort they are an indicator of a child’s ability to maintain attention.

functional vision

Saccadic eye movements are essential for reading efficiently. When reading the eyes need to make quick simultaneous and accurate movements from letter to letter and word to word, then at the end of the line, move to the start of the next line. Saccades require the brain to efficiently process the images from our central vision with our peripheral vision. The central vision to process the word, and the peripheral vision to tell us where to point the eyes next.

Symptoms of eye movement problems

  • Omission of words during reading.
  • Loses place when reading.
  • Uses finger to maintain place on page.
  • Word order switches.
  • Poor comprehension.

Focusing (accommodating) Disorders

Focusing is the eyes ability to see clearly at different distances. When looking into the distance our eyes tend to focus naturally without any effort. When we want to see clearly up close, a lens in the eye changes its shape to accommodate the light onto the correct part of the retina. This accommodative process requires more effort so our eyes can fatigue much easier when concentrating on near tasks. Children who are long-sighted require even more accommodative effort to see clearly, so they are more likely to develop an accommodative and / or vergence disorder. Accommodative disorders can be either accommodative insufficiency, accommodative excess or both, accommodative infacility.

Symptoms of focusing problems

  • Blurry vision particularly at near.
  • Eyestrain or headaches when reading.
  • Reading avoidance.
  • Close reading distance.
  • Reads for short durations only.
  • Tired eyes.

Ocular Alignment (Vergence) Disorders

To have clear single vision at all distance our eyes need to work together as a pair. If the muscles that control the eyes are properly coordinated then the image from the right eye is fused with the image from the left eye. Fusion of the two images leads to single vision and depth perception. A coordination problem can often present as blur or double vision especially for sustained close tasks. Children with poor ocular alignment may avoid reading, be easily distracted, or have trouble with concentrating and comprehension.

Symptoms of vergence disorders

  • Double vision.
  • Words move on the page.
  • Poor concentration and comprehension.
  • Reading avoidance.
  • Favours or closes one eye.
  • Blurry vision.