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EYE TRACKING IN READING / SACCADIC PRAXIS

How the eyes efficiently move left to right top to bottom in fluent reading

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Alan P Pearson OD PhD FCOVD

August 15, 2021


AT-A-GLANCE

  • Eye tracking in reading refers to the highly sequential left to right top to bottom eye movement pattern that is needed for fluent reading and good comprehension.
  • Saccadic praxis refers to how all of these functions come together in a coordinated way.
  • To diagnose eye tracking in reading difficulties takes testing that usually goes beyond a standard regular eye exam.   A Functional Vision Evaluation involves more involved functional testing of near point visual performance. 
  • Standardized tests and technology such as the Visagraph eye movement analysis help to determine if saccadic praxis difficulties are present.
  • Most often individual struggling with eye tracking in reading also have issues in two eye coordination, eye focusing, or basic eye tracking skills.  These issues need to be addressed first or at least treated simultaneously with the saccadic eye tracking concerns.   

EYE TRACKING IN READING

There are two kinds of eye movements, smooth pursuits and saccades.

Smooth pursuit eye movements are used to follow moving objects such as a baseball or an airplane in the sky. It is like the eyes are "locked on" to the object they are looking at, and smoothly follow the object wherever it moves.

PursuitSaccades

Saccade eye movements are used to look at multiple objects sequentially. The eyes look at one object and then quickly shift their gaze to another object. When the eyes are fixated or stopped on an object they visually feel the object to understand it. When the eyes are moving from one object to the next the brain must turn off the visual feeling processes, otherwise the whole world would appear to move or jump.

READING INVOLVES SACCADIC EYE MOVEMENTS

When reading text the eyes do not smoothly move across the page but rather make short jumping movements. When the eyes reach the end of the line they again must make a jumping eye movement, but this time in the opposite direction to the beginning of the next line in the paragraph. These jumping eye movements are called saccadic eye movements. If there are problems with these eye movements, it is very easy to lose one’s place.

Saccades

 

When reading, the eyes must fixate on a word, which involves visually GRABBING a word chunk with the FOCUSING and BINOCULAR SKILLS  and then VISUALLY FEELING the word chunk to understand it. After processing one word chunk the eyes have to let go and move to the next word chunk to repeat the process. This process has to repeat itself over and over. GRAB, FEEL, MOVE, GRAB, FEEL, MOVE, GRAB, FEEL, MOVE, ETC. This highly repetitive and sequential process has to happen smoothly and efficiently to be a good and fluent reader. As the word chunks are brought into the brain they have to be remembered and pieced together so that the reader understands the sentence, the paragraph, and then the whole story. Moving your eyes in this sequential way is not a natural skill. You must learn these eye-movements. How well you learn this highly specialized skill will influence how fluently you can read.

 

Reading

Difficulties can occur at many points along the way, which will result in severe difficulties in learning to read fluently. Here are some of the common problem areas:

  • FOCUSING SKILLS PROBLEMS:

    The eyes cannot visually grab the word chunks because of poor focusing skills and the person experiences blur, or words going in and out of focus. As the eyes are trying to focus, the visual feeling process is not happening, so no understanding is taking place.

  • BINOCULAR SKILLS PROBLEMS:

    The two eyes cannot visually grab the word chunks together as a team. One eye is looking at one word, the other eye is looking at a different word. The person either sees double or has to concentrate on one eye and ignore the other. When they switch their attention from one eye to the other, the words and text appear to jump or move, disorienting them so they lose their place, and the reading process is halted until they get reoriented. As soon as they are reoriented, their attention may shift again. Never being able to visually grab the words appropriately disrupts the visual feeling process and fluent reading becomes fatiguing, frustrating, or impossible!

  • VISUAL FEELING PROBLEMS:

    If the person is able to focus their eyes and binocularly coordinate their eyes, then the next step is to visually feel the word chunks for meaning and understanding. In a good reader this process takes place in less than one quarter of a second. This is too fast to analyze the letter structure of the word chunk and follow phonetic rules to figure out how the word should sound. The word has to be recognized visually as a whole word instantaneously. Ideally a visual picture should occur in the mind immediately. If a person cannot learn to visually recognize words instantly, then it may be due to a visual perception problem. Some people take the long and inefficient route of converting the seen word to the spoken word, then they listen to themselves in order to understand what was being read. Using this technique limits the reader to not much more than 200 words per minute reading speed, because that is about as fast as a person can talk to him/herself. Efficient readers can read up to 600 words per minute, but in order to do this they must convert seen words into pictures in the mind instantly without subvocalization.

  • EYE-MOVEMENT SKILLS PROBLEMS:

    Once the person is done looking at one word chunk, they must move their eyes to the next chunk. They must move their eyes just the right distance; not too far, since words may be missed, and not too short or pieces of words they have already seen are reread. People who have eye movement problems have difficulties establishing the repetitive sequential movement of their eyes and instead chaotically dart forward and backwards, bringing word chunks to the mind in a disorderly fashion. The mind then has the almost impossible task of sorting it all out to make sense of it. When confused, the mind directs the eyes to search for additional word chunks by re-reading, which contributes to chaotic and disorderly eye movements.

Saccadic Praxis is the term to describe how all of these pieces come together and a coordinated fashion so that the eyes can track from left to right top to bottom as necessary in fluent reading of the English language.

DIAGNOSING EYE TRACKING IN READING DIFFICULTIES

There are specific tests and technology that are used within a Functional Vision Evaluation to determine if there are difficulties with saccadic praxis or eye tracking in reading. 

The Developmental Eye Movement Test is a standardized test of saccadic eye tracking abilities and rapid automatic naming. The Vertical subtest involves rapidly calling a vertical column of numbers. This does not require significant saccadic eye tracking, but does require rapid naming skills. The Horizontal subtest involves rapidly calling of numbers arranged horizontally left to right, top to bottom, as in reading. This still involves rapid naming skills, but in addition requires precise saccadic movements and motor planning similar to reading. The final score is the error score which includes skipped numbers/lines, substitutions, additions, or transpositions. 

The Visagraph is an infrared eye tracking device that records where the eyes are pointing when engaged in silently reading a short paragraph. The device measures the average number of fixations (eye stops) per 100 words, the average number of regressions (backward eye movements) per 100 words, the average duration of each fixation, the reading rate in words per minute, the directional planing/pattern (left to right, top to bottom), the number of lines read/reread, and the cross correlation between the two eyes (related to binocular coordination). All of these scores are compared to grade level equivalent norms.

Only an eye doctor (Optometrist or Ophthalmologist) has the tools to perform a Functional Vision Evaluation and diagnose binocular instability. Not all eye doctors have the interest or training to perform a Functional Vision Evaluation.  If you are living in Washington State, USA near the Bellevue or Bothell area, you can schedule a Functional Vision Evaluation at the Vision Clinics of Development & Learning [www.visioncdl.com].  If you are reading this from afar, then the following directories can be helpful in locating a doctor who can perform a Functional Vision Evaluation:

College of Optometrists in Vision Development:  www.covd.org

Optometric Extension Program Foundation:  www.oepf.org

Neuro-Optometric Rehabilitation Association:  www.nora.cc

TREATMENT OF EYE TRACKING IN READING DIFFICULTIES

Most often there are underlying binocular instabilities that need to be treated prior to attending to the eye tracking in reading specifically, so our first goal is to make sure two eye coordination, eye focusing, and basic eye tracking are in place and working well.  To get to this goal, we first have to help the two eye coordination system converge the eyes and diverge the eyes appropriately and precisely to various distances.  We do the same in helping the eye focusing system (accommodation) focus and relax precisely to various distance.  Finally, we have put both eye coordination and eye focusing together simultaneously.   In the end we have therapeutically developed the ability to dynamically adjust and sustain two eye coordination and eye focusing during various stresses and eye movements that are encountered in a prolonged near point task (especially the left to right top to bottom eye tracking needed in fluent reading). 

Different vision clinics may have different protocols and some cases are more complex involving other issues than only eye tracking in reading.  The following are only typical guidelines at our clinic, and every case has to be considered individually.  Straightforward binocular instability with saccadic praxis difficulties usually responds well to a 4 to 5 month protocol that combines clinic visits once per week and prescribed home activities that take about 30 minutes per day five days per week.  At our clinic we use computer programs that send us data over the internet to coach and monitor the prescribed home activities.   The home activities are essential in our opinion for the successful treatment of this condition.   It is much like going to the gym for physical conditioning.  If you only go to the gym one day per week, you make minimal gains, but if you go to the gym 5 days per week you make tremendous gains.  Without appropriate home activities, vision therapy will take a lot longer to complete.  In some instances where a patient or family lives excessively distant from our clinic, we can get good results facilitating a home based treatment approach with only 1x per month clinic visits, but such an at-a-distance protocol has to be appropriate and is considered on a case by case basis.

In the first appointment you get your software and start working on the program at home.  Depending upon your situation the clinic visits are either half hour or one hour in length and occur one time per week.  A 4 to 5 month program will take about 16 in-clinic sessions to complete.  In addition to the treatment sessions there are three additional appointments called progress evaluations.  These occur about midway through the treatment, at the end of the treatment, and 3 months after finishing the treatment to make sure there are no regressions.

INSURANCE COVERAGE

Eye tracking in reading, saccadic praxis, and other techniques for improving overall reading fluency are considered by most insurance plans to be educational in nature and therefore not covered as a medical treatment alone.   More often, however, there are underlying issues in binocular instability that need to be addressed for adequate resolution of symptoms.  Treatment for binocular instability is considered medically necessary.

Binocular Instability, and more specifically the convergence insufficiency type,  is a condition that is increasingly covered by many insurance plans as there is a good research evidence concerning its identification and treatment.   This does not mean, however, that insurance coverage can be guaranteed.  Even with an insurance plan that says they "cover" treatment, you may still find there are large copays, deductibles, and coinsurance to deal with before you realize any benefit.  Almost no insurance plan will cover the entire costs for a treatment plan even if they say you have coverage.  For example, the software and other prescribed home therapy items and monitoring is usually paid privately or through a flexible spending account.   Also, even when an insurance plan covers the treatment sessions they typically only cover a 30 minute appointment.   Progress visits are medical doctor visits in general so they are more frequently covered with less problems.  

Some insurance plans have specific exclusions for "Vision Therapy" in which case they may cover once per month doctor's visits for an at-a-distance program, but they will not cover the in clinic treatment sessions.  You will have to look up the details of your insurance plan to determine if there are such exclusions.  Sometimes it is hard to find such information and it becomes necessary to call your insurance plan to ask them specifically.   Here is the question you can ask them that has the proper language and codes:  "Does my insurance plan cover vision therapy or orthoptics  92065 for a diagnosis of convergence insufficiency H51.11?"  and then ask "are there any exclusions of vision therapy for my plan?"  and finally ask:  "are there any prior authorization requirements?".   Remember, you have to first complete a Functional Vision Evaluation to reach an official diagnosis and prescribed treatment plan, and even if seems like it should be covered there can still be obstacles and coverage is never guaranteed.

NOTES

There are many other visual dysfunctions that can occur simultaneously with eye tracking in reading.   For example, binocular instability, strabismus, reflex problems, visual-vestibular problems, fixation and orientation problems, rhythm and timing problems, body knowledge/coordination problems, and visual perception and processing problems. Treatment of eye tracking in reading alone is not meant to address these problems. Some of these problems will need to be addressed before the eye tracking in reading treatment can begin. Some of the problems can be addressed simultaneously with treatment for eye tracking in reading.   The eye doctor will determine the best strategy, sequence, and emphasis in treatment plan selection.

www.visioncdl.com   info@visioncdl.com   425-213-1016

©2018 Vision Clinics of Development & Learning


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