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STRABISMUS, EYE TURNS, AMBLYOPIA AND LAZY EYE

Treatment Options for Cross eye, Wall eye, Esotropia, Exotropia, and Hypertropia

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Alan P Pearson OD PhD FCOVD

August 15, 2021


AT-A-GLANCE

  • Stabismus refers to eye turns inward, outward, up or down.  Eye turns can happen all the time, or some of the time.  Eye turns can involve one eye or alternative between both.
  • Amblyopia (lazy eye) is a blurry eye due to poor development.  It can occur due to a strabismus, but there are many eye turn situations that do not have amblyopia.
  • Strabismus occurs when the normal development of binocular vision is interrupted. 
  • Diagnosing strabismus or amblyopia can occur in a regular eye exam, but to really explore treatment options fully a more detailed analysis called a Functional Vision Evaluation is necessary. 
  • There are many treatment tools and options such as eye patches, surgery, prisms, or optometric vision therapy.  The proper tools and prognosis can differ widely depending on individual situations.
  •   At Vision Clinics of Development & Learning we use traditional tools and techniques for strabismus and amblyopia, and we also offer new technologies such as virtual reality software.   To be successful with any treatment program for strabismus and amblyopia will take daily practice.

TYPES OF EYE TURNS

The term strabismus means that one eye turns in, out, up, or down relative to the other eye.  Usually, one eye is looking at a target so it is considered the "straight" eye and the other eye is turned.   When an eye  is turning inward it is commonly called "cross eyed" but medically called esotropia or convergent strabismus.  When one eye is turning outward  it is commonly called "wall eyed" but medically called exotropia or divergent strabismus.   When one eye is turned up or down relative to the other eye this is medically called a hyper/hypo tropia or vertical strabismus.   You can see there are a lot of different names for the general category of eye turns.  

There are even more descriptive names for eye turns.

The words 'alternating'  and 'monocular'  refer to whether it is just one eye that is always turned, or if the turned eye switches between the right and left at times.

The words 'intermittent' and 'constant' refer to whether the eye turn happens only part of the time or is always happening.

For example Intermittent Alternating Exotropia involves one eye turning outward, away from the nose, relative to the other eye.  When this happens the brain is unable to see binocularly, with both eyes together as a team, resulting in double vision, suppression of one eye, and/or the inability to see 3D depth.  When it is intermittent it means the eyes do not turn all the time, but sometimes work together as a team.  When it is alternating it means that sometimes it is the right eye turning outward and sometimes the left eye is turning outward.  

When an eye turn is small and subtle, it may not be noticed by others, however, when it is more severe, the eye turn can be very obvious to others.  Apart from the cosmetic issues from a readily observable eye turn, eye turns also significantly impact functional vision leading to signs and symptoms such as  1) poor performance, attention, and efficiency in school or work, 2) pain, headaches, discomfort, double vision, dizziness, and general fatigue, 3) poor depth perception, coordination difficulties, posture problems, and poor sports performance, 4) specific reading difficulties such as loss of place, misreading, rereading, omitting words, jumping words, transpositions, and poor fluency, 5) avoidance of visually demanding tasks such as academics or near work.  For some individuals, the brain attempts to adapt to the misalignment of the eyes by learning how to suppress or ignore the vision in the turned eye.  While this helps eliminate double vision, it doesn't always relieve all symptoms and still results in poor visual function with no depth perception.  Because of the eye turn, other vision skills, such as eye focusing and eye tracking, may not be developing or functioning well, further impacting the individual's vision abilities, signs, and symptoms.

HOW EYE TURNS DEVELOP

When a child is born the brain is ready to learn how coordinate the two eyes together but it is not entirely hard wired to do so yet.  Just like learning to walk involves the baby having important and expected experiences before walking is mastered, two eye coordination expects important visual experiences to happen early on in order to develop good two eye coordination.  Think of the developing visual system like a train track.  The two rails represent the right eye and the left eye.  The ties represent the developed two eye coordination neurology that keep the two eyes coordinated.  When a baby is born, the path is ready, but the track and ties are not yet fully laid down.  Early experiences and development is a process that is like building out the two eye coordination train track down the path. Each eye develops onward, but equally important is the development of the ties that coordinate the two eyes together as a team.

An eye turn or strabismus develops when something gets in the way of the development of normal binocular vision; as if something is blocking the construction of the train track. 

   Because a child's brain is very adaptable and development must move forward regardless, what happens is that visual development will take a detour to get around the blockage.  But this often means that one or both eyes must deviate away from the straight path and they start to develop independent paths on their own, without the development of the important ties that keep the eyes coordinated. 

If both eyes are used and developed independently, then each eye can see sharp and clear, but one eye is turned relative to the other.  In this case we have simple strabismus or eye turn.    If only one eye is used and developed then the other eye gets left behind and does not develop the ability to see sharp and clear even with the best eyeglass lens.  This is more complicated and called "amblyopia" or "lazy eye" together with the strabismus or eye turn.  

The key points here are that developing good two eye coordination involves development of each eye's vision together with the neurological ties that hold the two eyes together in a coordinated way.

DIAGNOSING EYE TURNS

Regular routine eye exams emphasize eye health and eye optics and while they usually can identify and diagnose strabismus and eye turns they do not often delve deep enough into the issue to develop a treatment plan.   In order to function well, the eyes need  to be healthy and any need for eyeglasses should be taken care of.  Next, a Functional Vision Evaluation will take an in-depth assessment of the strabismus and/or amblyopia in order to determine treatment options.

As mentioned before eye turns come in many different variations based on factors such as the direction of the turn (inward, outward, or up/down), frequency of the eye turn (all the time, or sometimes), whether it is one eye or the other (monocular or alternating), and whether other issues such as amblyopia (lazy eye) or poor depth perception are present.  All of these factors help the doctor determine when and how the strabismus likely began and what the treatment options and prognosis are for resolving the situation. 

Only an eye doctor (Optometrist or Ophthalmologist) has the tools to perform a Functional Vision Evaluation.  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
[Schedule Appointmment].

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 TURNS

When amblyopia (lazy eye) is present traditional eye patches are often used for a couple hours per day on the better seeing eye to force development of vision in the lazy eye.  While this can help vision be more equal between the two eyes, traditional eye patches do nothing to help build the neurological ties that coordinate the two eyes together.  If a child is awake 12 hours per day, and using an eye patch for 2 hours per day, then they are still getting 10 hours of developmental practice with the better eye independently of the lazy eye.   Eye patching strategies can be a tool for treatment, but are usually never a full solution.

Strabismus surgery involves removing one or more of the muscles around the eyes and reattaching them to a different position on the eyeball so that the eyes will appear straight.  This is like moving the tracks onto the main path.    But surgery cannot create the neurological ties that hold the two eyes together in a coordinated fashion.  The eyes may look straight, but they may not function together in coordination so depth perception may still be poor or entirely absent.   After the surgery a child may learn to coordinate the eyes by building some neurological ties, but other children may learn to simply turn the eye in the same way they did before the surgery as a way of re-adaptation back to the more comfortable position they are used to.  Surgery can be a tool for treatment, but it is not always a full solution. 

Prism glasses involves the use of optical prisms to bend light.  These kinds of eyeglasses will allow eyes to remain in their turned position, but function as if they were straight and coordinated.  But prisms do not instantly create the neurological ties that hold the two eyes together as a team.  Prisms might help to provide the opportunity to develop better to eye coordination ties, but this doesn't usually happen without some thoughtful planning and intervention by the doctor; and such a process has to be monitored and adjusted closely.   Prisms can be a tool for treatment, but they are not always a full solution.

Optometric vision therapy involves returning to the developmental stage where the eyes started to deviate, and from there using specific visual stimulation to help the development of each eye's vision together with - and this is most important - the neurological ties that coordinate the two eyes together as a team and provide the opportunity to see 3D depth.   Optometric vision therapy is an intervention to provide the developmental experiences that were missed due to some sort of early blockage that caused the eye turn in the first place.  Two eye coordination and 3D depth perception is not an all or nothing experience.  Just like vision can function over a continuum between sharp and blurry, two eye coordination and 3D depth happens over a continuum between fine precision and less precision.   Blurry vision can still be very useful even if it is not perfectly clear, and  two eye coordination and depth perception can be very useful in life even if it functions with less than maximum precision.  As optometric vision therapy progresses,  and the neurological ties are successively laid down, two eye coordination and depth perception can improve along the continuum towards more precision and better function.   

Optometric vision therapy is not a single tool, rather it is a recognition that all of the tools have merit in certain situations when one is attempting to develop and improve two eye coordination.  Therefore, the optometrist may recommend eye patching, surgery, or prism glasses at certain stages, but the optometrist's toolkit is not limited to only these tools.  Optometric vision therapy is a recognition of the full scope of science and clinical experience with the aim towards maximizing the possibility and precision of developing useful two eye coordination and 3D depth perception in cases where it has not been developing normally and an eye is turning.  Optometric vision therapy does not work 100% of the time (no treatment does) but the research clearly demonstrates that it is much more successful than doing little or nothing.  

An exciting new strabismus treatment tool available at Vision Clinics of Development & Learning is Virtual Reality technology.  In Virtual Reality headsets each eye is looking at a different screen, therefore we can change the position and content of each screen independently.  This makes it possible to create a virtual world where it is much easier for two eye coordination and depth perception to develop.  Once skills have developed in the virtual world we can then slowly transition toward maintaining the skills in more real world situations.  Virtual reality is a great tool, but it doesn't entirely replace the tried and true traditional techniques used in vision therapy.

INSURANCE COVERAGE

Strabismus, eye turns, amblyopia and other binocular instabilities are conditions that are increasingly covered by many insurance plans as there is a good research evidence concerning 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 so they are more frequently covered with less problems.  

Some insurance plans have specific exclusions for "Vision Therapy" but they may cover once per month doctor's visits for an at-a-distance program.  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 strabismus or amblyopia?"  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 strabismus or amblyopia.   For example, 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 turns alone is not meant to address these other problems. Some of these problems may need to be addressed before the strabismus treatment can begin. Some of the problems can be addressed simultaneously with treatment for strabismus or amblyopia.   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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