Assessment and treatment of Saccade Problems

Saccades – The Quick Movement of the Eyes

Saccades are quick short movements of the eyes. The cavemen used them to quickly assess the environment and see where a threat (or dinner) might be. We use them now for reading, in a series of quick movements and fixation. We also use saccades to update changes in our environment, so they are influenced by peripheral awareness.  They help build a spatial map of the environment. The movements are involuntary and triggered by changes in the spatial environment.

One can look for inaccurate saccades associated with TBI, concussions and strokes. Inaccurate saccades are also associated with most binocular vision problems, like convergence insufficiency.

Measuring the Saccade Problem

Saccades testing can show a therapist overshooting or undershooting, but objective measurement helps set goals.  We use the Developmental Eye Movement test. The DEM provides good objective data concerning eye movement accuracy.

The Developmental Eye Movement test (DEM), is a standardized assessment of saccade accuracy. It is standardized for 5-13 year olds. An adult version is currently being developed and tested, but testing indicates values for a 13 year old are generally valid for an adult. 

The DEM has 4 parts, all involve the timed reading of a list of numbers. The first part is sample of horizontal numbers used to insure the patient can see the text adequately. In the next section, two vertical columns of numbers are read and timed with errors noted.  There are two vertical tests with the times added.

There is the final horizontal test which present horizontal lines of unevenly spaced numbers, which the subject reads while being timed with omissions and substitutions noted.

Times are compared to norms based on age or grade percentiles, They are then used to derive a ratio of horizontal to vertical times that help to identify the cause of the errors, either automatically (subjects ability to call out numbers) versus ocular motor difficulty.

The test is quick and correlates well to reading problems.

The DEM is not perfect as the person must be verbal and recognize numbers. Frequently the task of reading out loud produces a lot anxiety for children that have problems with the task also. Observation of behaviors during the DEM and the reading can also give some insight.

The tester should note…

  • does the child hold the material very close to his face ?
  • …or far?
  • does he squint or rub his eyes during the assessment?
  • does he use his finger to follow the letters?
  • does he move his head during testing? This is very telling as using head movement rather than eye movement slows fluency and saccade accuracy.
  • are there long pauses at the beginning of a new as the child attempts to find the correct line
  • does accuracy of words get worse as the reading continues or does the child use context to fabricate the end of the sentence?
  • Does he turn his head to the left or right?

Following reading, I ask some specific questions if the child had difficulty to help identify what the child is seeing. These questions sound crazy, but make perfect sense to child with saccade or near vision problems.

  • do the words move when try to read them?
  • do you see double?
  • do they blurry then clear then blurry?
  • do they appear to float?

Sometimes the children have a hard time describing just what they see. Parents are often very surprised at the responses to the questions. The child did not know that everyone does not see that way.

Treatment

The treatment for saccade problems, like all ocular motor problems, assumes the child is in best corrected visual acuity.

I also use a sheet or graph paper with random dots for the children to draw small , vertical lines through.

The Hart Chart Decoding activity is also a good task.  This task has a grid of letters on one sheet and themed (there’s SpongeBob and Sports, and others)secret messages on another. Each letter in the massage corresponds to a column/row combination that the child counts to find the letter. Initially the child is allowed to use his finger to help count the rows and columns, but as they get better at the task, the finger is no longer allowed.

EyeCanLearn.com   is an amazing website with vision games and printable with saccade activities.

Having a child read the first letter of words in a paragraph can improve saccade accuracy as well simple vertical strips of letters that can be more further apart. The therapist can add a metronome to these tasks to help increase the pace.  Add balance to these task to increase the challenge of the brain and visual system.

Saccade strips are two strips of paper with vertical letters. The patient reads the letters left to right and top to bottom. Start with the strips close together then separate them as the the patient gets quicker. Remember to keep the head still, even if the therapist has to help!

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Assessing Eye Movements

Assessing Eye Movements

As therapists, we should assess EOM or extra ocular movements, the optometry term for eye range of motion. Looking at these movements can give information about brain and cranial nerve function as well as help identify limitations on functional tasks like reading .

Eye movements use similar names as other movements with inferior being downward, superior being upward, lateral movements described as duction with adduction  moving toward the nose (nasal)and abduction away from the nose (temporal). Optometry also has vergence, which is the movement of both eyes toward the nose (convergence) or away from the nose (divergence). Smooth convergence and divergence is important in the near focusing system.

With the patient seated and focused on a point about 40 cm away, the eyes should be still. This is called fixation.  A small rhythmic movement, called nystagmus, is a sign of a central nervous system problem. It is often associated central nervous system problems like Multiple Sclerosis.  It is a frequent early sign of the disorder. It is also closely linked to the vestibular system and the patient might report dizziness. When congenital, the brain adjusts to movements as in the video below.

Congenital Nystagmus

9 points of primary gaze are assessed having the patient follow a point to left/right/up/down/up left/low left/upright/low right. The eyes should move together through all of these points.

9points of gaze_normal_540

Assessing Cardinal Gaze

Each of these movements is control by cranial nerves and failure of an orbit to move in a direction could be a sign of cranial nerve problem or a muscle problem. This occurs frequently as a result of brain injury or trauma to the eye or orbit. This can also be congenital. This eye turn is referred to as a strabismus.  Strabismus causes diplopia or double vision. They can be improved with prism by an optometrist or possible surgery to shorten or lengthen the muscle by an ophthalmologist.

To assess convergence use the near point convergence test. In this assessment, a target held about 1 meter from the patient’s nose and slowly brought toward the nose. The patient is instructed to tell the tester when they see two of the targets. The target should get to within 6cm to be considered “normal”. The test should be done 5 times with the final result be the distance at which the child saw double on this final trial. Reduced convergence is not uncommon following brain injury and stroke and is linked to reading difficulty in children. Reduced convergence makes near vision tasks more difficult as the brain has work harder to see clear. This is called convergence insufficiency. The condition even has its own  website.  This has also become more common in adults we put demands on our near vision system with increased use of smart phones.

Near Point Convergence test

In tracking, the patient follows a target in a circular pattern, both clockwise and counter-clockwise making 2 revolutions each direction. Tester notes the number of fixation loses, the smoothness of the movements and the ability of the eyes to move together.

Eye Pursuits or Tracking

Saccades are very quick eye movements of very short duration. It is a series of fixations and saccades that allows one to read efficiently. Inaccurate saccades are frequently associated with poor reading skills. Optometry can improve saccade accuracy and improve reading .  Saccades testing has the patient fixate from one point to another with the tester noting adjustments following the fixation and if the eyes move together. We can perform the Developmental Test of Eye Movement  or the King-Devick for objective testing of eye movement.  Saccade accuracy can be an indicator for possible concussion as well.

Saccade testing

Abnormal EOM tests should be referred to optometry for complete assessment. They are often related to central nervous system problems, cranial nerve palsy’s or cerebellar problems. They are common in stroke and brain injury survivors and cause decreased reading ability, balance and depth perception.  Patients frequently suffer with eye movement problems for years following a stroke or brain injury, but with the right tools, they can be improved improving a patient’s functional ability.

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