Impaired Motor Skills of Children with Anisometropia and Strabismus

The latest research from the prolific group at the Retina Foundation of the Southwest, including Krista Kelly and Eileen Birch, involving motor skills in children with strabismus, has been published in Investigative Ophthalmology & Visual Science. Dr. Fortenbacher previously blogged about research from this group as it pertains to amblyopia.

The key conclusion from the new paper is as follows: “Amblyopia and strabismus disrupt the development of motor ability in children. These findings highlight the widespread effects of discordant binocular input early in life and the visual acuity and binocularity deficits typical of these eye conditions.”

Children involved in the study ranged from age 3 – 13, and had a history of strabismus or anisometropia, with or without amblyopia. The researchers evaluated fine and gross motor skills during binocular viewing using the Movement Assessment Battery for Children, Second Edition (MABC-2).

Tasks for the Manual Dexterity, Aiming and Catching, and Balance Subscales in the MABC-2 were reported as follows:

The authors note that discordant binocular input during infancy and childhood may disrupt the ability to use these cues during motor development, which is evident by their finding of poorer performance with an infantile onset of the eye condition. Children with anisometropia in their study had a later mean age at diagnosis than those with strabismus . Although better binocularity in anisometropic children likely contributed to the lack of deficits seen for the Aiming and Catching and Balance subscales, the later onset of anisometropia may also play a role.  Children with normal stereoacuity and normal depth of suppression in their study did not score lower than controls on any subscale, consistent with earlier studies showing better motor performance in those with recovered binocularity and suggesting that binocularity is essential to task performance. 

We are going to be featuring this article on Elsevier’s Practice Update Eyecare this week, and in my comments I observe:

This adds to the growing body of evidence that the impairments in strabismus and amblyopia are associated with more than deficits in visual acuity, stereoacuity, and binocular integration.  It also has implications for the importance of assessing successful outcomes in the treatment of these conditions beyond surgery, occlusion, or atropine penalization.  The nonamblyopic group included only strabismic children aligned within 6 prism diopters of orthotropia at the time of testing, which means that they would have been considered “cured” according to traditional criteria yet could potentially benefit further from low amounts of prism or other forms of therapy to aid binocular integration.  Nor did the authors find any correlation in children with amblyopia between the depth of amblyopia and the extent of motor abnormalities.  The conclusion therefore is that a fundamental disruption in binocular development, irrespective of the extent of amblyopia, underlies the motor abnormalities observed.  As the authors review, this has pervasive effects from ball-playing to early academic skills, and therefore warrants more comprehensive assessment and treatment.

Introducing the new VisionHelp Strabismus Library

It is with great pleasure to announce the launch of the latest VisionHelp initiative, the brand new VisionHelp Strabismus Library.

This new site brings together a compendium of content that includes Videos, Presentations, Books, Research and much more, dedicated to the diagnosis and treatment of Strabismus. This was created as a place for advanced understanding of strabismus, consolidated into an organized and easily accessible location. Many thanks to the VisionHelp Strabismus project Chairperson, Dr. Katie Davis and project team members Dr. Len Press and Dr. Nancy Torgerson.

The VisionHelp Strabismus Library, which provides a resource for public and professional understanding of a serious binocular vision problem that affects millions of people worldwide, comes as the fourth in a list of initiatives that began first with the VisionHelp Concussion Project, followed by the VisionHelp Amblyopia Project, followed by the VisionHelp Vision and Learning Project. 

In addition, as one more step to further improve and streamline the entire collection, the VisionHelp Group has consolidated these initiatives, each into their own Library and housed them in the newly designed VisionHelp website

Therefore, on behalf of the Mission of the VisionHelp Group, we hope you will join with us and share this collaboration of content to help end the senseless struggle due to developmental and rehabilitation vision problems.

Dan L. Fortenbacher, O.D. FCOVD

The Shape of the Sky…Repairing Strabismus and emotional healing a focus of MVTSG 2020

Strabismus, as outlined by the American Optometric Association Clinical Practice Guideline, CPG-12, is a failure of binocular vision (eye teaming) that is typically recognized as one or both eyes that turn inward (esotropia) or outward (exotropia) and/or up or down (hyper/hypotropia) that occurs in about 3% or 1 in 30 individuals worldwide. But, the impact goes much deeper into the life of the person with Strabismus than just an obvious cosmetic appearance, which has its own serious impact on the emotional wellness of the strabismic individual.  

Research published in the American Journal of Ophthalmology, entitled: The effects of strabismus on quality of life in adults shows, that individuals with Strabismus (either with and without double vision) have many quality of life and emotional side effects that begin in childhood and continue throughout adulthood including but not limited to:

  • Poor depth perception
  • Reduced self confidence
  • Difficulty interpersonal relationships
  • Poor driving skills
  • Negative feelings
  • Poor reading ability
  • Difficulty with eye contact 
  • Anxiety

To bring this important information  to an audience of doctors and vision therapists, the Annual Michigan Vision Therapy Study Group Meeting (MVTSG-2020) took place in Grand Rapids, Michigan on January 24-25, 2020 focused on the theme of Strabismus and Amblyopia. Presenters came to speak on these topics from around the US, Internationally and throughout Michigan and was the largest attended MVTSG meeting in it’s long history.

Kicking off the meeting was one of the world’s leading experts on the vision therapy management of  Strabismus and author of the new book, The Shape of the Sky, Dr. David Cook. He outlined new techniques and methods for helping patients (adults and children) with strabismus to gain the ability to rapidly gain the ability to point the two eyes together, eliminate double vision and gain depth perception.

Our Wow Vision Therapy Grand Rapids Team, Dr. Alyssa Bartolini, Dr. Peter Silman and Collin Welsh, COVT,  presented on the performance and emotional factors that affect the lives of those with Strabismus  and outlined a comprehensive model of treatment using a top down (executive function) along with advanced office-based vision therapy including virtual reality in vision therapy at home. The results of this model of treatment has not only resulted in significant outcomes, for adults as well as children, in their binocular vision and development of depth perception for better coordination daily activities and driving, but has also had a dramatic effect on their confidence and emotional quality of life.

The Michigan Vision Therapy Study Group is recognized as a legendary 1.5 day vision therapy educational meeting  that has taken place every year in the month of January in Michigan for the last 4 decades. It is a volunteer project with the intent of bringing together doctors and vision therapists with a passion for collaboration, teaching and expanding understanding of methods for helping patients to acquire better vision development through vision rehabilitation and vision therapy.

This year’s team of presenters were: Dr. David Cook, Dr. Bradley Habermehl, Dr. Dan Fortenbacher, Dr. Alyssa Bartolini, Dr. Johann Schlager, resident, Dr. Peter Silman, resident, Cheryl Dortch, COVT, Collin Welsch,COVT, Dr. Mohamed Moussa, Abeer Ahmed, MBChB and vision therapists, Amina Weed and Monica Fehrs,  Dr. Stephanie Enriquez and vision therapists, Dr. Steven Ingersoll, Dr. Luke Lirones, resident and  Dr. Paula McDowell.

Michigan Vision Therapy Study Group – 2020


Dan L. Fortenbacher, O.D., FCOVD


The Sandwich Approach to Vision Therapy and Strabismus


Our good friend and colleague, Dr. Nancy Torgerson, who has established a model synergistic relationship with the surgeon Dr. Thomas Lenart, reports that the term “sandwich approach” seems to be gaining traction in the Pacific Northwest for the combination of vision therapy and strabismus surgery to boost clinical outcomes in certain cases.  This might consist of vision therapy prior to strabismus surgery to optimize sensory readiness for motor fusion, and/or post-surgical therapy to stabilize or safeguard binocular vision.

As I’ve blogged before, the implications of providing enhanced patient outcomes through  this individualized and synergistic approach are enormous.  There are signs that more practices may be leaning in this direction.  As an example, Northwest Eye Surgeons posts on its website: “The goal of strabismus treatment is to improve eye alignment so that the eyes work together (binocular vision). Treatment addresses the underlying cause and may include eye glasses, eye exercises, prism therapy, vision therapy and/or eye muscle surgery … Strabismus, like many other conditions, requires an individualized treatment plan. Your doctor will assess your eye condition, develop a treatment plan with you and keep you informed as your treatment progresses.”

To date there have been isolated case reports in the literature about combination or sandwich approaches of optometric vision therapy providing a more optimized outcome of strabismus surgery, such as this one on cyclic esotropia.  A compendium from the Royal College of Ophthalmologists notes the role of non-surgical exercises for convergence insufficiency, distance esotropia and symptomatic phorias.  You would think that the sandwich approach might be a natural subject for a group like PEDIG to study, and as collaboration in clinical practice grows this may occur one day.


In building the sandwich approach I’m reminded of the need for “entente cordiale” in the early treatment of squint (the British term for strabismus), as related in this classic 1977 article in which Pigassou wrote: “Orthoptic treatment has its place in the current therapy of all functional and developmental troubles. The principles are the same as those on which the treatment of the other functions is based, and in particular the troubles of general motricity. It is virtually possible to transpose the directives of Bobath on the early treatment of cerebral palsy to the early treatment of squint, keeping in mind that in cerebral palsy there are organic lesions and that in squint in normal children the perturbation has a functional origin.”

Perhaps the greater impetus for entente cordiale these days actually stems from the drive toward strabismus treatment in adulthood.  Consider this perspective on adult strabismus published by the American Academy of Ophthalmology:  “In the management of adult strabismus, the detailed sensory assessment provided by an orthoptist is crucial in determining the prognosis for achieving or maintaining single vision. The orthoptist can also assist in determining prism power when treatment with prisms is indicated, can offer eye exercises to build fusional amplitudes when appropriate, and can provide accurate strabismus measurements for surgical planning when muscle surgery is indicated.”

A landmark paper authored by McBain and colleagues makes it clear that much remains to be learned about bridging the gap between clinical criteria for success in strabismus and how patients feel about their outcomes.  We believe that the sandwich approach may hold the key in that regard.

Strabismus: A Neurodevelopmental Approach

This year marks the 25th anniversary of one of the best-kept secrets in ophthalmologic literature.  The slim volume I’m referring to reads more like a bound Ph.D. thesis than a book, and I recall skimming it 25 years ago in the SUNY library when it was published thinking: “Hmm … this is interesting”, but left it at that.  Apparently so did the rest of the field, because I don’t recall having come across it in the ensuing years.  So I treated myself to a copy through  a bookseller’s marketplace, and was delighted to rediscover it.


John T. Flynn is a pediatric ophthalmologist known primarily for his work in ROP, but wrote this book as a vision quest of sorts.  Convinced that strabismus is principally a design flaw in the development of the central nervous system rather than a localized problem originating in the eye muscles, Dr. Flynn’s book contains a number of passages that should resonate with you beginning with the first page:

“My topic, strabismus, has fascinated and perplexed me (among many others) for over a quarter of a century.  Often in despair of ever understanding anything about the topic, I have put aside inquiry into the many questions patients present when I examine them and have resorted to a mechanical way of thinking about the condition that persists in its worst form as sterile dogmatism – ‘if the eyes are in turn them out, and if they are out turn them in’.  But my demon will not go away.  And so it is that I have come to write this book.”

Toward the end of his introduction, Dr. Flynn continues:

“By now, I hope the reader has noted that I refer to strabismus as a visuomotor anomaly and I will continue to do so throughout this text.  The reason is to keep ever in mind the dual nature of strabismus.  We would not experience the phenomenon of vision as we humans do unless both parts of the system functioned as one.  This whole approach was aptly expressed for me in another context by von Monakow: ‘we see with our whole brains’.”

In deriving a generic model of strabismus, Dr. Flynn comments:

“Strabismus occurs, then, during the last stages of development of the visuomotor system. It is unaccompanied by other major neurological disorders, so  exclude here as well from consideration the strabismus that accompanies cerebral palsy states and other major neurological disorders of the neonatal and infant period.  That does not mean that strabismus in unaccompanied by other central nervous system developmental problems: rather, these other problems are more subtle and must be looked for in a different context than we are used to.”

What I interpret Dr. Flynn to mean is that exceptional forms of strabismus stem from diffuse motor control issues, as evidenced by the high percentage of children with CP how have misaligned eyes.  But the majority of patients seen in clinical vision/eyecare practice present with CNS developmental problems that are more subtle.  This is borne out as he elaborates his neurodevelopmental theory (p. 46):

“Strabismus is a specific response to an insult/injury of the central nervous system that, most importantly, occurred in a specific period (time) of development of the visual system and that may have both genetic and epigenetic components … The reason for the delay in appearance s not apparent but may involve the maturation of components of the visual nervous system coupled with environmental factors that as as triggers to elicit the clinical symptomology …”


Bear in mind that Flynn’s attribution of the importance of environmental influences on the expression of strabismus was written 25 years ago, long before the role of epigenetics was appreciated and we daresay is still under-appreciated in the eyecare profession.  Flynn should also be acknowledged for pondering the potential influences of therapy deeply:

“First, the observed behaviors or characteristics of strabismus are the external manifestations of the dysmorphology of the central nervous system which is the results of developmental injury.  Second, careful study of the strabismic patient’s behavior, both sensory and motor, yields important insights into the nature and extent of the injury that produced the strabismus … Third, because of the very global nature of central nervous system development, careful study of the strabismic patient will yield evidence, though probably subtle, of defects in development of other systems, for example, auditory, somasthetic, motor, and early developmental learning, which, although mild, nevertheless accompany the developmental defect we recognize as strabismus.”

Flynn insightfully views the preponderance of strabismus in infancy being in the esotropic direction as a timeline during which the developmental process went awry earlier, as opposed to a primary muscular imbalance in the lateral recti.  Similarly he views the ocular motor abnormalities that accompany infantile esotropia as signposts of the failure of primitive neural circuitry to be pruned back after synaptogenesis to a more efficient, flexible, and adapted normal circuitry.  Think about that for a moment:  abnormal OKN, VOR, and DVD as persistence of primitive reflexes in the CNS manifest in the ocular motor pathway at the level of the eyeballs.  Flynn then proposes an intriguing basis for looking anew at strabismus (p. 64), and one that we might dub quantum strabismus:


“We begin, for didactic reasons only, by separating sensory and motor, not because there is any real separation between them – we see with our shoe visuomotor brain.  Rather, the duality of the system is enforced by our primitive conceptions of how the system works.  It is much like the wave-particle duality of the photon of light or the electron; both viewpoints must be kept in consciousness to fully understand the behavior of the entity, though one aspect of its behavior may best be explained by employed one or the other frame of reference.  So it is with strabismic dysmorphology: Its behavior is best accounted for clinically by examining it from the universal viewpoint of excess or surplus of connections that we postulate are excitatory and reciprocal in nature, which means that a type of instant reversibility exists between the disconnected areas.”

This naturally leads Flynn to accept that their can be co-variation in correspondence regarding spatial localization, and readily resolve apparent paradoxes in clinical response to normal vs. anomalous correspondence based on testing conditions.  This prompts him to call the question that should be on the mind of his fellow surgeons (p.78):

“Second, we need to know what manipulations of motor behavior, other than surgery, will  change correspondence.  Will manipulation of the accommodative, convergence, optokinetic, and/or vestibular systems change localization behavior?  What is the relationship between induced errors of localization (by surgery), so-called paradoxical diplopia, and the postoperative behavior of eye movements?  How do these two variables change with respect to each other over time?”



Psychosocial Issues Surrounding Strabismus Surgery

“It should be remembered that strabismus surgery can realign the eyes but does not always realign the damaged psyche of a patient who has undergone long-term negative evaluation because of their strabismus.”  This quote, from the discussion section of a recently published paper in JAAPOS sounds like a revelatory breakthrough for surgeons.  And then one reads the sentence that follows:  “It may be that strabismus surgeons should consider preoperative psychosocial interventions for patients who appear to have unrealistic expectations of surgery and poor psychosocial well-being in order to improve outcomes postoperative outcomes.”

The paper is authored by McBain and colleagues, presented as the Philip Knapp Lecture at the 40th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Palm Springs, California, April 2-6, 2014.  It is part of a theme that the group has been exploring for the past few years, but one that includes considerations of therapy only in the form of prisms for diplopia or botulinum therapy to wedge muscles when surgery fails (see here).  The gist of it is that at least some patients undergoing surgery for strabismus should undergo psychologic or psychiatric evaluation pre-surgically to temper their post-surgical expectations.  No mention of pre-surgical assessment of the brain’s preparedness to deal with the shock therapy of realignment, yet alone pre-surgical therapy to deal with the sensory-motor sequelae.

It is a theme that Sue Barry has called attention to extensively since 2006.  And most recently Susanna Zayarsky, whose newly published book I have been reading and re-reading to gain deeper insights from the patient’s perspective.  I wonder if McBain and colleagues have read either Fixing My Gaze, or would be interested in reading One-Eye Princess?  What I do know is that there isn’t a single reference to anything optometric in their article.  And that, my friends, is as big an issue as the issue itself.


ADDENDUM October 21, 2016:  This newspaper article in The Mercury News regarding Susanna and her book.

Susanna Zaraysky on VT & Strabismus

Congratulations to VT advocate Susanna Zaraysky on the publication of her new book, One-Eyed Princess: Gaining depth in sight and mind.


I certainly don’t expect you to recall, but I blogged about Susanna in 2011 as someone who learned about optometry and vision therapy through the Oliver Sacks piece in The New Yorker magazine about Stereo Sue in 2006.  I first encountered Susanna through the Sovoto Adult Strabismus forum, and encouraged her to share her feelings about the psychological aspects of strabismus therapy more widely.  I just found out about the book through Susanna’s post on Sovoto a few days ago, and immediately ordered a copy of her book.  I anticipate that she’ll elaborate on the thoughts and experiences she shared in 2011, and will anxiously await my B & N package in the mail!

In the interim, here is a superb interview that Susanna did last Friday on CBS-TV in San Francisco with Michelle Griego, of Bay Area Focus.

Pattern Recognition in Strabismus


Arianna’s mother works for a local optometrist, Dr. M.  She has gradually progressed in myopia, and he tried to fit her with CRT lenses but her corneal astigmatism got in the way of success.  She currently wears soft lenses and had been complaining of blur in her right eye.  Her sphere power is -7.00 in the left and -5.50 in the right, and when she presented on her most recent exam with 20/40 acuity in that eye, Dr. M. was expecting to increase the minus lens power in that eye but any higher minus that what she already had created double vision.

When conducting binocular testing through her habitual Rx, I noticed that Arianna would elevate her chin slightly in order to maintain fusion.  When I asked her to tip her chin downward, she reported diplopia.  I asked her mother if she had noticed that Arianna preferred to look at things downward and she said: “Sure – I keep asking her why she looks down so much when she’s using her phone or a tablet.  Arianna – show the doctor how you look at your phone!”


Further testing revealed why Arianna has such a difference depending on her angle of gaze: “A” pattern esotropia, with the inward turn of the right eye increasing in upgaze and eliminated in downgaze.



At our conference to review the findings, we agreed to hold the minus power the same in the right eye and prescribed optometric vision therapy to expand Arianna’s range of fusion.  We considered prescribing base-up yoked prism at the outset to enable Arianna to maintain a more normal head posture, but she preferred not to use a spectacle Rx initially and to accomplish as much as she could without it.  I anticipate that Arianna will do very well, and that in the future she’ll find plenty of other reasons to hold her head high.


Does Strabismus Surgery Improve Quality of Life?

And the answer is of course, it depends!

But … depends on what?  After all, it has been reported that nearly half of adult patients  who undergo strabismus surgery do not feel that the outcome has improved their QoL, or Quality of Life.  (Hatt SR, Leske DA, Liebermann L, Holmes JM. Comparing outcome criteria performance in adult strabismus surgery. Ophthalmology 2012; 119: 1930-1936.)

gauge_needle_max_18436A couple of years ago we blogged about the work of McBain and colleagues at City University London regarding the psychosocial factors in strabismus.  Now the same group has extended their work with a new publication in the journal Eye titled:  Does Strabismus Surgery Improve Quality and Mood, and What Factors Influence This?  

Eye Journal Cover

Here is a key comment from the discussion section of their paper:

“Surgery deemed partially successful was found to be more psychologically detrimental, leading to a reduction in psychosocial quality of life from pre- to post surgery.”

There are several ways to look at the results, primarily reported in the tables of the paper that frankly aren’t easy to decipher.  One is that the clinical outcomes themselves don’t relate to the patient’s perception of improvement in QoL.  The limitation to this conclusion is that the data does not include any sensory measures other than the report of diplopia.  But even if one considers the change in cosmetic alignment before and after surgery, it would be understandable that patients with high expectations prior to surgery might be disappointed with the post-surgical results.  Further there are adults who have the perception of their eyes not working together that still plagues them after surgery, and they often feel that others can sense this residual abnormality.

It still mystifies me why strabismus surgeons don’t collaborate more often with optometrists on pre-surgical factors that might optimize post-surgical outcomes.

The Eigenvalues of Strabismus

Sue Barry and I gave a joint lecture at ICBO in England last year which encompassed in part the emotional valence of strabismus, and she continues to blog elegantly about components of vision that we tend to take for granted.  McBain and colleagues in the U.K. just published an article in the British Journal of Ophthalmology that touches upon QOL issues for which conventional criteria for cure of strabismus is inadequate.  Only the abstract of the article is available through open access.

The article revolves around a questionnaire and provides this conclusion:  PCA revealed a 3-factor solution for the Expectations of Strabismus Surgery Questionnaire (ESSQ): (a) intimacy and appearance-related issues, (b) visual functioning, (c) social relationships. This 3-factor solution explained 59.30% of the overall variance in the ESSQ. Internal consistency, content and nomological and concurrent validity were considered acceptable.


I don’t fully understand the statistical analysis used in the paper, and chances are that unless you’re a mathematician or statistician you won’t fully grasp it either.  Irrespective of the eigenvectors involved, there are several important points noted in the body of the article.

1) The individual items of the questionnaire indicated that patients expected surgery to lead to considerable improvements, primarily in relation to the appearance of their eyes as well as vision, and more specifically double vision. Research, however,does suggest that only 24% of patients with strabismus are successfully realigned post surgery according to clinical criteria; while 38% are classified as partial successes or failures. This might be because the patient requires prism therapy or a patch that was not necessary prior to surgery.  They still have a large deviation, or are experiencing double vision, visual confusion or other related visual symptoms that may have developed after surgery.

2) Of the 124 participants with diplopia prior to surgery in this study, one patient expected their double vision to worsen, 7% expected their diplopia to remain the same and all others expected their double vision to improve. Research does, however, suggest that double vision can remain in approximately two-thirds of patients up to 6 months post surgery, with almost one-fifth of patients with horizontal residual deviations still finding diplopia problematic in daily life.  This highlights a possible discrepancy between what the patients expect in relation to their double vision prior to surgery and what may actually happen. This potential discrepancy could contribute towards poor quality of life or poor satisfaction post surgery, and is particularly pertinent considering that patients appear to be more successfully aligned according to clinical criteria as opposed to quality of life outcomes.


The bottom line is this:  patients with strabismus often have expectations for life after strabismus surgery that isn’t fully anticipated by their surgeons.  Might collaboration with optometrists skilled in working with many of these visual factors result in better outcomes addressing these quality of vision and life factors?