Visual Perception

Of visual perception

There are many assumptions made about a student’s performance on visual perception tests. After all, these tests give norm’ed results which can be helpful in goal making and identifying a potential cause for an academic problem.

But do the results actually reflect visual perpetual skill?

Many factors can hamper the reliability and validity of visual perceptual testing.

  • Visual acuity-is this patient in best correct visual acuity? Have they had an eye exam and been prescribed the appropriate glasses? Do the glasses fit well to allow for the intended benefit?
  • Binocular vision skills?-Poor binocular vision skills can result in double vision and blurred vision up close which can affect the results of visual perceptual testing?

These two factors, when not corrected, make for a “garbage in-garbage out” situation and taint the results of the testing, increasing the likelihood for invalid results in the patient.

Imagine putting a glove on a patient then asking that patient to identify coins that they are holding in the gloved hand. They would have a difficult time doing this, not because of an inability to process the feel of the coin, but because the stimuli to be interpreted is muted. It becomes difficult to process to the correct conclusion when the initial stimulus is faulty.

Behavior and cognition matter too

With best corrected acuity and good binocular visual skills, other factors, such as attention can play a role in visual perceptual testing. Common visual perceptual tests can take as long at 45 minutes of monotonous testing making even the most attentive children bored and possibly affecting results.

Most visual perceptual tests are designed so the child with a visual perceptual problem misses three consecutive items in a section, then advance forward to the next section. The pattern is irregular (child misses one item then 3 correct then misses two items, then one correct) perhaps attention is playing a role in the test results.

Visual Percetual Testing

In my clinic, I do not test visual perception until after binocular vision issues have been corrected and the patient is in best corrected visual acuity.

With these things in place, you will find visual perception intervention much more effective and testing will be more valid and reliable.

Learn More

Learn more about this subject in a live course presented by Robert.  Its now available as a webinar too!! Hosted by PESI Education

 

 

Sensory Modulated Postural Dysfunction

Posture and Vision

The magnocellular tract plays an important role in posture. It provides visual information that allows for spontaneous adjustment of posture and muscle tone as the environment changes. Integration of vestibular information with this visual information helps keep us stable when are moving.

Think of standing on a boat gently pitching to and fro on the water. As the boat rock, the muscles of ones legs, trunk, and neck all compensate and adjust to allow you to stay standing. Imagine how hard it would be to do this if one were blindfolded. It would be much more difficult if the brain was unable to get accurate data about the changes in horizon and the incoming waves.

Sensory Modulated Postural Dysfunction

SMPD is one of the subtypes of sensory dysfunction described by the Star Institute. Marked by postural weakness and decreased stamina (what we may have described previously as “low tone”), these children have difficult times sitting up tall and may demonstrate a head-forward, flexed posture with shoulder rolled forward and possible scapular winging. They may have weak hands and present to OT for difficulty with handwriting or visual motor integration. In optometry, they call this postural dysfunction or other terms.

Posture is Vision Is Posture

The link between posture and vision is very important. Decreased visual acuity or decreased magnocellular awareness can cause the brain to get poor information about the body’s position in space and not allow for appropriate muscular corrections as the environment changes and the child moves.  The vestibular system as well requires visual input to allow for correct adjust adjustment of posture. We might observe this as a clumsy child or a child with weak posture.

As therapists, it is important that we make sure our young patients have a full and complete eye exam as we begin to address postural weakness, visual motor integration and handwriting problems. An uncorrected visual system will make treatment very difficult. But an appropriate visual system becomes a powerful tool to help correct these problems.

Vision as a Postural Tool

It is possible to make use of the powerful magnocellular system to help with posture. The addition of prism or binasal occulsion during a typical treatment for postural problems and “low tone” can alter the perception of visual space. Base down prism will shift visual space upward, making the head go up. When the goes up, the trunk moves into more extension. The brain quickly makes adjustment to the body based on the altered visual space.

Can they see?

I continue to find children with a full team of professionals: PT, OT SLP, ABA, pediatricians, etc,  that have not had an eye exam. Know the ODs in your town that perform comprehensive binocular vision exams and make sure your kiddos can see !!

Learn More

Learn more about this subject in a live course presented by Robert.  Its now available as a webinar too!! Hosted by PESI Education

About the Author

“When should we see no head movement during visual tracking?”

When should they hold their head still…

The development  of the visual system in children is much discussed. The AOA offers time lines which have development of eye movement continuing to improve at 36 months. This development is dependent upon many factors including the development of the brain as whole and the vestibular, and proprioceptive systems. The development of these systems is inter-dependent. Problems in the visual system will affect development of the vestibular and other systems and impact the developmental movement sequence. This is why the first eye exam is recommended at 6 months of age.

In the birth to 3 three year old, developmental delays would most likely include tracking and saccades problems, particularly when neurological problems (seizures, anoxia, CP, etc) are present. As therapists, our treatments should should stimulate as many sensory systems at possible, including vision.

Eye Movement norms

The best information on the development of eye movement accuracy comes from the NSUCO Ocular motor norms. The NSUCO protocol looks at ability to perform the movement, accuracy of the movement, amount of head movement present and the amount of body movement present during the testing of tracking and saccades. Each of these skills is rated 1-5 with each score defined in the above referenced article. This is the standard way saccades and tracking are quantified by ODs. Each movement would include 4 numbers describing the child ability to perform the movement. This is a somewhat subjective test, much as our manual muscle testing is somewhat subjective. It is most important for the therapist to recognize the errors and refer to the doctor for scoring, then be able to interpret the score as provided by the doctor.

The norms begin at age 5 and support the idea of a constantly improving ocular motor system until full maturity at the age of the 10. The paper further references minimal standards from age 5 to 10 to help identify less than age appropriate eye movement accuracy.

The Therapist’s job

We should be screening these eye movement on all of our patients. Children with developmental delays have a high incidence of ocular motor problems which affect balance, reading, spatial awareness, fine motor and visual motor integration development. These ocular motor problems are influencing the outcomes of our interventions so being testing them should be a part of every OT and PTs evaluation process.

Learn More

Learn more about this subject in a live course presented by Robert.  Its now available as a webinar too!! Hosted by PESI Education

About the Author

ADHD and Eye Movements

ADHD and Eye Movements

There is much research concerning the link between eye movements and ADHD. Researchers consistently find specific eye movement behaviors associated with ADHD. But how does this research help in the clinic?

ADHD and Saccades

Much of the ADHD/Eye movement research has focused on the quick, exploratory eye movements called saccades. Children diagnosed with ADHD show saccade accuracy consistent with their peers. They are able to quickly and accurately look to a new target in the environment. When instructed not to look a target (anti-saccades), children with ADHD have a more difficult time NOT looking at the stimulus (1). Reading is a series of quick fixations and saccades that affects reading speed. These saccades improves reading fluency in children(2) . Children with ADHD also show reduced tracking ability which further affects reading fluency (3)  (4).

Near Vision and ADHD

Convergence Insufficiency, an eye movement disorder affecting one’s ability to maintain clear near vision, is found at three times the rate in ADHD children compared to those not diagnosed with ADHD(5).  A study also shows that children with symptomatic convergence insufficiency score higher (more negative behaviors) on an academic behavior scale then those children diagnosed with ADHD (7). So convergence problems can be associated with ADHD-like behavior problems.

ADHD and Optometry

Optometry is aware of the link between eye movements, behavior and academic performance. ADHD symptoms can mimic the behavioral signs of eye movement problems, even when a child is unable to vocalize the vision problems he is has having. Treatment of convergence problems is also known to reduce the symptoms of ADHD reported by parents (6). Treating saccade and tracking problems also helps to improve reading fluency and improve academic performance.

Only a complete evaluation by an optometrist that specializes in eye movement problems can help identify these problems that could be limiting performance in a child with ADHD. Treatment of these problems with in-office vision therapy can help improve a child’s academic performance.

Learn More

Learn more about this subject in a live course presented by Robert.  Its now available as a webinar too!! Hosted by PESI Education

About the Author