Download Deitz, K - American Academy of Optometry

Kelsey Deitz
Pediatrics and Vision Therapy Resident
Southern College of Optometry
Topic: Post-Strabismus Surgery Outcomes
Abstract Title: Consecutive Exotropia Post Strabsimus Surgery With Unusual
Outcome Due To “Built-In” Monovision Prescription
Abstract Text: Patient has surgery for esotropia and later presents with a constant
left exotropia in the distance but a constant right exotropia at near.
I. Case History
•Patient demographics: 15-year-old Asian male
•Chief complaint: Patient presents for a binocular vision workup/vision therapy
evaluation secondary to a longstanding outward eye turn in both eyes. The timing is
described as constant, and the context is at both distance and near. The patient was
referred after a contact lens evaluation the previous day. Rare diplopia was noted
when probed and was explained as only occurring when patient is “spacing out.”
•Ocular, medical history
- Last eye exam was in 2014
- History of strabismus in both eyes in 2001. Surgery was performed in both eyes in
2002. The patient and parents were told later that he may need a repeat surgery, but
no other surgery has been done to date.
- Refractive History: Single vision spectacles for full time wear. Patient is currently
being fit for a CRT lens in the myopic left eye.
- Last medical exam in 2015 with no abnormal findings.
- All review of systems is negative.
- No known allergies
•Medications: none
•Other salient information: Patient scored a 27 on the COVD Quality of Life checklist,
with most frequent symptoms dealing with difficulties with ocular motility
(misaligning digits/column numbers) and binocularity (head tilt/closing eye when
reading, trouble keeping attention on reading). Any score over 20 is significant for
visual problems.
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II. Pertinent findings
•Clinical
- Distance visual acuity (VA) cc: 20/15 OD, 20/20+2 OS, 20/15 OU; Near VA OD, OS,
OU 20/15-2
- Pupils and Confrontation Visual Fields: normal
-EOMs: full range of motion; diplopia reported in inferior gaze and when crossing
the midline
- Cover Test: Distance 20 constant left exotropia, Near 20 constant right exotropia
- Habitual Rx: OD +0.50-0.50x085, 20/15; OS -3.00-0.75x145, 20/20; reports
wearing glasses for the past 5-8 years
- Manifest Rx: OD +0.50, 20/15; OS -2.75-1.00x145, 20/20
-Stereo: No global or local forms appreciated; alternately suppressed, switching
between both “R” and “L” in suppression check
- Worth-4-Dot: Distance showed crossed diplopia in light and dark conditions; Near
showed OS suppression in light and dark conditions (deep suppression)
-Near Point of Convergence: receded; break/recovery 11cm/20cm, 8cm/21cm,
15cm/25cm
-Vergence Ranges: low BI at near, all other findings normal
-Ocular motility: NSUCO below average (low accuracy) for pursuits and saccades;
DEM with average findings but likely suppression of right eye at near
-Anterior Segment: Chronic allergic conjunctivitis OU
- Posterior Segment: healthy findings in both eyes
•Physical: N/A
•Laboratory studies: N/A
•Radiology studies: N/A
•Others: N/A
III. Differential diagnosis
•Primary/leading: Consecutive exotropia
•Others: Convergence insufficiency, Divergence excess
IV. Diagnosis and discussion
•Elaborate on the condition
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Exotropia is a manifest outward eye turn that can cause diplopia if either
suppression or harmonious anomalous correspondence is not seen. Suppression is
the sensory anomaly that is seen most frequently with exotropia, but anomalous
correspondence and amblyopia can also occur. (Clinical Management of Strabismus,
Caloroso and Rouse).
With a frequency of constant strabismus, it has been found that not even a
frequency of 660 seconds of arc disparity can be appreciated on random dot
stereograms (Clinical Management of Binocular Vision, Scheiman and Wick). The
treatment plan in exotropia has an overall approach of starting with motor
processing and then extending to sensory processing (Clinical Management of
Strabismus, Caloroso and Rouse).
•Expound on unique features
What is particularly unique to this case is that this patient developed a prescription
that effectively gave him monovision, with one nearsighted and one farsighted eye.
Unlike imposed monovision as an option in presbyopic patients, this patient actually
fully suppressed (and turned out) the eye that was not beneficial at each given
distance. This takes an extreme toll on the binocularity of his system, causing
essentially no depth perception. However, this patient was still able to obtain 20/20
vision in each eye at both distance and near. The reason for this may be due to the
image size differences between the two eyes causing disparity. It will be interesting
to see whether the CRT lens fit in the left eye will change some of these findings, as
the left eye will no longer be nearsighted compared to the right.
V. Treatment, management
•Treatment and response to treatment
- Patient is currently being fit in a CRT lens in the left eye to attempt to equalize the
refractive status between the two eyes
- Week 1: refraction of left eye shows -1.00-1.00x145. The patient was told to
use current lens every night for 2 weeks before reassessment.
- This patient has been referred for vision therapy, with his first session scheduled
on 09/09/2015. The goal of VT for this patient is to work on anti-suppression,
binocularity, and ocular motility.
•Refer to research where appropriate: N/A
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•Bibliography, literature review encouraged:
- Consecutive exotropia may occur many years after esotropia surgery. Lateral
rectus recession with advancement of the previously recessed medial rectus is an
effective treatment. An exotropic drift occurs after consecutive exotropia surgery, so
aiming for a slightly esotropic alignment is appropriate. (Donaldson M, Forrest M,
Gole G. The surgical management of consecutive exotropia. J AAPOS:230-6.)
- A postoperative correction of orthotropia was the only predictive factor for
improvement of stereopsis in adults with childhood strabismus. (Andalib D, Nabie R,
Poormohammad B. Factors Affecting Improvement of Stereopsis Following
Successful Surgical Correction of Childhood Strabismus in Adults. Strabismus 2015:
80-4.)
- Medial rectus slippage is common in consecutive exotropia, but medial rectus
advancement is an effective treatment. Consecutive XT surgery is associated with
late exodrift, so it is not necessarily a permanent solution. (Leon B, Demer J.
Consecutive exotropia: Why does it happen and can medial rectus advancement
correct it? Journal of American Association for Pediatric Ophthalmology and
Strabismus. (n.d.))
VI. Conclusion
•Clinical pearls, take away points if indicated: A variety of findings can occur post
strabismus surgery that don’t necessarily follow any specific rule or trend. Each
patient may develop adaptations to use their eyes in an efficient manner, or in a way
that makes sense to an individual’s system. For this individual, the effectiveness of
vision therapy will vary based on the stability of his adaptation to using both eyes
together. This may end up creating a less stable system for him which would lead to
a difficult prognosis.
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