Strabismus and Sensory Adaptations
Timothy Hug, OD, FAAO
Assistant Professor – Ophthalmology
University of Missouri-Kansas City School of Medicine
Children’s Mercy Hospital
Kansas City, MO
[email protected]
Strabismus
n 
Esotropia
n 
Congenital / Infantile
n 
Accommodative
1
Esotropia – Congenital
(Infantile)
n 
Esotropia – Infantile
Onset : age 6 – 18 months of age
n 
n 
n 
Angle of Deviation 30^ - 40^ or greater
n 
Helveston (1983) - found mean average of 40^
n 
Von Noorden (1985) - found mean of 50^ - 60^
Monitor
n 
Spontaneous resolution in 27 % for patients with onset less than 20 weeks
(Congenital Esotropia Observational Study – AJO, 2002 Jan 109-118)
Refractive errors tend to be same as age matched non strabismics (+1.00 +2.00)
Esotropia – Infantile
n 
Imagine then the infantile et…
n 
Few binocularly driven cells…
n 
Surgical realignment…to promote binocular driven cell development
n 
How long can we wait?
Binocularity “turns on” …suddenly …between 3 -5 months of life - Reflex
(Birch E., Wang J: Stereoacuity Outcomes Following Treatment if Infantile and Accommodative Esotropia; Optome
Vis Sci 2009 Jun; 86 (6): 646-652)
So what happens in presence of an anti binocularo-genic factor
n 
Think similar to amblyogenic factor during the amblyogenic time period
What is the binocularogenic time period?
Congenital et studies…evolution from 1980s – 2005…change of thinking from age 2 years…to under
2 years, to less than 6 months from onset of deviation (malcom ing…eilen birch)…to even 2 months
after onset (Ken Wright reported 100% of infantile ET operated at 4 months of age achieved motor
fusion)
Hubel and Weisel…strabismic cat during first 12 weeks of life (cat’s
binocularogenic time period)
more cells develop that are not binocularly driven
Esotropia Infantile
Management
Surgery
n 
n 
n 
n 
What is sensory adaptation to the misalignment?
Timing of Intervention
n 
Surgery by 6 – 24 months of age (CEOS)
n 
Surgery within 2 – 4 months of misalignment
Promotes best chance for development of stereopsis (24-36%)
Tychsen T, Can Ophthalmologists Repair the Brain in Infantile Esotropia? Early Surgery,
Stereopsis, Monofixation Syndrome and the Legacy of Marshall Parks. Journal of AAPOS, vol 9
(6), December 2005, 510-517.
Wright K, High-grade Stereo Acuity After Early Surgery for Congenital Esotropia. Arch
Ophthalmology vol 112, July 1994, 913-919.
Birch E, Stager, D, Random Dot Stereoacuity Following Surgical Correction of Infantile Esotropia.
J Pediatric Ophthalmology & Strabismus, vol 32, July 1995, 231-235.
Ing M, Outcome Study of Stereopsis in Relation to Duration of Misalignment in Congenital
Esotropia, J of AAPOS vol 6, February 2002, 3-8.
Murray D, Changes in the Functional Binocular Status of Older Children and Adults With
Previously Untreated Infantile Esotropia Following Late Surgical Realignment. J AAPOS, vol 11,
April 2002, 125-130.
2
n 
n 
n 
Marshall Parks – facultative supression
(foveal vs extrafoveal)
n 
Or not!
ARC – as described by Marshall Parks
n 
No surgery/ delayed surgery
After surgery for the misalignment…the peripheral binocular system takes over
and allows development of peripheral fusion with a microtropic alignment status
n 
Animal models suggest decay of the interocular cortical connections
n 
n 
n 
n 
n 
Animal models suggest the length of the horizontal axon connections
corresponds to the misalignement of 4 – 8 prism diopters
Lack of proper binocular cortical development prevents future binocularity
improvement…
n 
If not microtrope …no fusion…no fusion potential
Parks M A, Sensory Adaptations in Strabismus; Harley’s Pediatric Ophthalmology, 5th Edition; Nelson,
Olistsky; Lippincott Williams & Wilkins, Philadelphia: 137 – 142
n 
No chance of “restoring” something that is not there
Parks, M A, The Monofixation Syndrome; Tr Am Ophth Soc, vol 67, 1969: 609-655
n 
Why?
Tychsen, Lawrence: Can Ophthalmologists Repair the Brain in Infantile Esotropia? Early Surgery,
Stereopsis, Monofixation Syndrome, and the Legacy of Marshall Parks; Journal AAPOS, Dec 2005;510-517
Infantile Esotropia
Summary
Esotropia – Accommodative
n 
Age of Onset – 4 -12 months
n 
Refractive
n 
Angle of Deviation – Greater than 30 prism diopters
n 
Onset 18 – 36 months1,2,3
n 
Surgical re-alignment goal: within 2 months of onset
n 
Refractive Evaluation – normal for age
n 
Amblyopia treatment
n 
Best stereo outcome requires intervention 2 – 6 months after onset of deviation
n 
Associated uncorrected hyperopic refractive error :
+4.00 average
n 
Angle of Deviation : 20 - 30 prism diopters at distance
n 
Amblyopia possible – depending on time of decompensation and treatment
n 
50% of accommodative ET with High AC/A ratio decompensate into non
accommodative
Birch E., Wang J: Stereoacuity Outcomes Following Treatment if Infantile and Accommodative Esotropia; Optome Vis
Sci 2009 Jun; 86 (6): 646-652
Tychsen, Lawrence: Can Ophthalmologists Repair the Brain in Infantile Esotropia? Early Surgery, Stereopsis,
Monofixation Syndrome, and the Legacy of Marshall Parks; Journal AAPOS, Dec 2005;510-517
Esotropia – Accommodative
n 
n 
Refractive - management
Cycloplegic refraction
n 
Prescribe full cycloplegic both eyes
n 
Prescribe less than full plus
n 
1
n 
2
n 
3
Basic and Clinical Science – Pediatric Ophthalmology and Strabismus 2008-2009
Eye Care for Infants and Children – Bruce Moore, OD
Rutstein R, Update on accommodative esotropia, Optometry, 2008; 79, 422-431
n 
1
n 
2
n 
3
Basic and Clinical Science – Pediatric Ophthalmology and Strabismus 2008-2009
Eye Care for Infants and Children – Bruce Moore, OD
AOA – Optometric Clinical Practice Guidelines
Esotropia – Accommodative
n 
n 
Refractive - management
Re-evaluate esotropia after spectacle wear
n 
One month? One week?
n  Orthophoria at Distance and Near
n  Reduced but not eliminated angle at near and distance
n  Reduced or Eliminated angle at distance with esotropia at near (high
AC/A ratio)
3
Esotropia – Accommodative
n 
Parent Preparation
n 
Full time wear of spectacles
n 
Angle may appear worse with out glasses, after adaptation
n 
Follow up refraction every 4-6 months for 1 – 2 years (depending on age)
n 
If controlled with spectacles – surgery not an option
n 
n 
n 
n 
n 
n 
n 
n 
n 
Back to ET
Anti Binoculaogenic factor during a critical age
Similar to infantile ET delay period?
What if parents don’t even bring child in?
n 
n 
79 % of patients reviewed had orthophoria or esotropia of 10 prism diopters or less
5% had decompensation
Hussein M, Weakly, D, Wirazka t, Paysse E; The long term outcomes in children who are
non compliant with spectacle treatment for accommodative esotropia; Journal of AAPOS, vol
19 (2), April 2015: 169-171
Fair and poor compliance with spectacle use greatly increases risk of poor sensory and
motor outcomes in children with pure refractive accommodative esotropia
What if parents don’t comply with glasses wear?
n 
n 
Kanwar M, Sharma A; Long-term results of accommodative esotropia; Journal of AAPOS, vol
18 (3), June 2014: 261-265
n 
n 
Age 18 -36 months? Binoculogenic age?
Hussein M, Weakly, D, Wirazka t, Paysse E; The long term outcomes in children who are
non compliant with spectacle treatment for accommodative esotropia; Journal of AAPOS, vol
19 (2), April 2015: 169-171
Fair and poor compliance with spectacle use greatly increases risk of poor sensory and
motor outcomes in children with pure refractive accommodative esotropia
What if patient has (inappropriate) surgery ?
n 
Will not develop perfect binocular function
n 
Probable amblyopia
n 
Once patient has amblyopia…significant decrease in binocular potential
n 
n 
Mohan, K, Sharma, A: Long term results of accommodative esotropia; J AAPOS, vol 18 (3):
261-265
79 % had orthophoria or microtropia
What if wrong glasses prescribed or worn?
Accommodative Esotropia
Summary
n 
So imagine the 30 ET, who is 5 year old with refraction of +5.50 OU
n 
n 
n 
n 
Will they be aligned in glasses?
Is it too late for steropsis?
n 
n 
Onset 12 -24 months
Associated with uncorrected hyperopia
Potential for good alignment, good stereopsis, good acuity
if……………………………………………………………………………….
4
Exotropia
n 
Exotropia
n 
Congenital
n 
Intermittent
n 
Convergence Insufficiency
n 
Divergence Excess
Exotropia - Congenital
n 
Onset 6 – 12 months of age (Harley’s Pediatric Ophthalmology and Strabismus)
n 
Rare – 1.0% occurrence (Cohen 1985)
n 
Angle of 35 prism diopters (average)
n 
Treatment:
n 
Manage amblyopia if exists
n 
Manage refractive conditions if outside age matched normative
n 
Surgery within 2-6 months of onset
n  Similar to congenital esotropia – allows potential for restoration of
binocularity
(Hunter D, Long term outcome of uncomplicated infantile exotropia, J
AAPOS, 2001, 5, 352-356)
Exotropia - Intermittent
n 
Onset – between 6 months and 4 years of age
n 
Most common form of exotropia
n 
If late enough onset from intermittent to constant, then binocular development
can / will be normal…
n 
Sensory adaptation is supression (for intermittent)
n 
Suppression for constant
n 
n 
May break down to constant deviation (unknown percentage – Nelson; Harley’s
Pediatric Ophthalmology and Strabismus, 2005,158-162)
Facultative (Parks) vs Absolute
Strabismus Surgery
n 
n 
Form vs Function
n 
Pediatric vs Adult
Imagine though the binocular cortical cells are developed…intact and
mature ..now just “dormant”
n 
Awaiting binocular stimulation via orthoptics or surgery,
n 
Poof! stereopsis
5
Strabismus Surgery
n 
n 
Form vs Function
Pediatric
n  Misalignment of eyes results in compromise of binocular
cortical regions (Hubel and Weisel)
Strabismus Surgery
n 
Form vs Function
n 
Does critical window exist for this benefit?
n 
n 
n 
Realignment of eyes may result in recovery of some
binocular cortical function
Studies indicate best chance within 2 – 4 months of misalignment for
congenital esotropia
(Tychsen T, Can Ophthalmologists Repair the Brain in Infantile Esotropia? Early Surgery, Stereopsis,
Monofixation Syndrome and the Legacy of Marshall Parks. Journal of AAPOS, vol 9 (6), December 2005,
510-517.
Wright K, High-grade Stereo Acuity After Early Surgery for Congenital Esotropia. Arch Ophthalmology vol 112,
July 1994, 913-919.
Birch E, Stager, D, Random Dot Stereoacuity Following Surgical Correction of Infantile Esotropia. J Pediatric
Ophthalmology & Strabismus, vol 32, July 1995, 231-235.
Ing M, Outcome Study of Stereopsis in Relation to Duration of Misalignment in Congenital Esotropia, J of
AAPOS vol 6, February 2002, 3-8.
Murray D, Changes in the Functional Binocular Status of Older Children and Adults With Previously Untreated
Infantile Esotropia Following Late Surgical Realignment. J AAPOS, vol 11, April 2002, 125-130.
Strabismus Surgery
Strabismus Surgery
n 
Form vs Function
n 
Form vs Function
n 
When does “no chance” exist?
n 
Adult
n 
Can adult strabismics ever recovery some binocular cortical function?
n 
May depend on status of binocularity at age of “binocular maturation”
n 
Strabismus Surgery
n 
n 
n 
Form vs Function
Strabismus Surgery
n 
Traits evaluated
Honesty
n 
Attentiveness
Humor
n 
Communication Skills
Intelligence
n 
Competency
Leadership Ability
n 
Dependability
Organizational Skills
n 
Emotional Stability
Sincerity
Adult
What if there is no chance of binocular function?
Kushner B, The Benefits, Risks and Efficacy of Strabismus Surgery in
Adults; OVS, vol91 (5), May 2014
6
Strabismus Surgery
Strabismus Surgery
n 
Overall, the strabismic faces were judged significantly more negatively,
across 11 descriptive characteristics, than the non-strabismic face.
Psychosocial aspects of strabismus study.
Satterfield D, Keltner JL, Morrison TL
Arch Ophthalmol 1993; 111:1100-5
n 
CONCLUSIONS: Psychosocial difficulties are a problem for teenagers and adults.
Correction of strabismus in the older teenager or adult may offer them
improvement in psychosocial functioning
7