STRABISMUS
Kenneth W. Wright, MD, Director, Pediatric Ophthalmology, Cedars Sinai Medical Center, Los Angeles, CA
| STRATEGIES FOR MANAGING INTERMITTENT EXOTROPIA
|
| Intermittent exotropia (XT): very common, large-angle exophoria controlled by fusional convergence;
normal fusional convergence 25 to 30 prism diopters (PD); divergence amplitudes 6 to 8 PD; typical intermittent
XT patient—eye drifts out with fatigue or daydreaming; in phoria phase, bifoveal fusion and stereopsis
excellent; in tropia phase, hemiretinal suppression, and diplopia rare; quantitate dissociation by
changing luminance; neonatal physiologic XT—most neonates born with XT; worsens over time; according
to von Noordon, 75% progress, 10% remain stable, 16% improve; manifests during daydreaming, with alcohol
and sedative use, and in severe illnesses; squint to bright light; amblyopia rare (acquired problem;
most of time, eyes straight with good stereoscopic vision)
|
| Classification: basic—same distance in near (D=N); true divergence excess—look in distance, eye goes way
out, look up close, eye straight (D>N); pseudodivergence excess—look in distance, eye goes way out, look up
close, eye straight; in 30- to 60-min patch test, near deviation increases (D>N); convergence insufficiency—
cannot converge straight in distance (N>D)
|
| Examples: intermittent XT—typical patient with straight eyes; cover eye, eye goes out; patients suppress; XT
deviation acquired after 5 or 6 yr of age results in double vision; anomalous retinal correspondence reported
(not seen by speaker); occasional suppression or double vision; pseudodivergence excess—D XT 30, N XT
10; patch for 30 min and remeasure, now D XT 30, N XT 25; patch test dissociated tonic near convergence
and brought out full deviation; operate at 30, knowing N XT is 25, not 10; otherwise, undercorrecting;
patch test important in patients with more XT in distance than near; true divergence excess—D XT 30, N XT
10; patch test 30 min to determine whether true or pseudo; now D XT 30, N XT 12; big discrepancy; must
be careful; operating for 30 makes them esotropic at near; will have constant double vision at near; always
tell patients they may see double after surgery; goal to make patient slightly esotropic (usually goes away; if
not, bifocals needed); measurement of variable angle—patch test; use far distant fixation object to bring out
full deviation
|
| Nonsurgical treatment: part-time occlusion; patch dominant eye few hours daily (antisuppression); wakes
up deviated eye; not cure; delays surgery; overminus causes overconvergence; overminusing not good outcome;
prisms or fusional convergence training for convergence insufficiency; eyes straight in distance, XT
at near; high hypermetropia with XT—patients very farsighted and do not accommodate or converge; treat
paradoxically with full plus, then able to see clearly and converge; >3 to 4 D; small angle; children <4 yr of
age—do not operate unless really breaking down
|
| Surgical indications: increasing tropia phase; history important; eyes out >50% of time good marker (red
flag); with relative indication, no need to rescue (fusing most of time); cosmesis; diplopia (rare); bilateral
lateral rectus (LR) recession preferred procedure for all deviations; “V” pattern—XT looking up; straight
looking down; childhood strabismus plus V pattern is inferior oblique (IO) overaction; move laterals away
from apex; can perform bilateral LR recession and IO weakening procedure; composites—up/down and
right/left; A pattern looking down; superior oblique (SO) overaction; lamna pattern; not much change in up
to primary; primary to down gaze goes out; SO only muscles abduct in down gaze; be careful not to weaken
SO (can cause torsional double vision after surgery); surgically move laterals down; postoperative
management—6 PD esotropia (ET) good after surgery; younger patients with small-angle ET will suppress
and develop amblyopia; try not to operate on children <4 yr of age, unless breaking down; use baseout
prisms in glasses in patients with persistent consecutive ET at 2 wk postoperative and symptomatic double
vision; reoperate at 2 mo if no improvement; residual XT—same as preoperative indications; convergence
insufficiency—prescribe correction if mildly myopic; congenital XT—rare; congenital cranofacial problem;
some underlying systemic disease (eg, neurologic, albinism, craniofacial)
|
| Accommodative convergence/accommodation (AC/A) ratio: look at amount of convergence for any
given amount of accommodation (focusing); to focus one third of meter, focus 3 D; clinical distance-near
relationship (Parks method)—abnormal if deviation changes >10 PD from distance to near; normal AC/A
ratio 4 to 5; lens gradient method—changes accommodation by lenses, not fixation; heterophoria method—
changes focus by changing view from distance to near; uses interpupillary distance measurement (very
important); use centimeters, not millimeters; speaker always uses lens gradient method; used in accommodative
ET; examples—XT 30, put up -2; converge to straight; AC/A ratio 15; XT 5 with -3, ET of 10
(overconverges), change of 15 PD and AC/A ratio 5; high AC/A ratio—use bifocals for straight eyes in
distance and ET at near; always use +3; provides comfortable near vision in young patients
|
| Surgery for accommodative ET: indicated when glasses do not work; residual strabismus for distance acquired
problem; has binocular fusion potential; can be straightened; “don’t sit on kids”; “do not wait, and
get them straight”; perform surgery after 2 refractions with ET in distance; operate for deviation greater
than residual; prism adaptation—neutralizes deviation; keep increasing prism until deviation stabilizes;
expensive; requires multiple visits; speaker prefers to use augmented surgery; better results; operating
between deviation with and without correction
|
| Infantile accommodative ET: onset at 2 to 12 mo; full hypermetropic correction; surgery if residual ET
with correction; Bruckner test—bilateral red reflex test; brighter reflex from deviated eye (light bouncing
off peripheral retina)
|
| Criteria: large-angle ET in first 6 mo of life; child does not use eyes together during critical period of development;
poor potential for fusion; develop latent nystagmus and dissociated vertical deviations
(DVDs); give patient full plus, immediate full plus if >3
|
| Presentations: Duane’s syndrome—left eye does not get out; lid fissure narrowing on adduction; Ciancia
syndrome—cross fixator; tight medial muscle (also seen in Mobius syndrome); classic cross fixator with
big ET; Mobius syndrome—believed to be 6th nerve palsy; big angle ET; IO overaction, DVD, and latent
nystagmus associated with congenital ET; fast phase to fixing eye in latent nystagmus; optokinetic nystagmus
(OKN) asymmetry (smooth pursuit asymmetry)—lifelong poor diminished nasal to temporal nystagmus
with good temporal to nasal nystagmus; occurs 100% of time in congenital ET; Congenital Esotropia Observational
Study (CEOS) trial—patients with large-angle ET during first 6 mo of life seen on 2 examinations
2 wk apart with no hypermetropia, only 4% resolve spontaneously; children do not get better on own
|
| Surgery: preoperative considerations—hypermetropia, amblyopia, ductions; if >3 D, try glasses; look for oblique
dysfunction; goal—peripheral fusion at best; why poor outcomes?—patients born stereoblind; motor
misalignment disrupts neural development; ET rapidly disrupts binocular cells in 3 to 4 mo; very early surgery
might improve binocular vision; earliest surgery (bimedial recessions [5.5-6 mm]) conducted by speaker
on infant 13 wk of age; started fusing 1 day postoperatively
|
| Limited eye movements: weak LR muscle (paresis) or tight medial rectus (MR) muscle (restriction); either
restriction or paresis when eye shows limited movements; signs of restriction—“dog on a leash” (eye moves
fast, stops abruptly); good saccades; positive forced duction; increased intraocular pressure; signs of
paresis—positive force generation test; have patient look out, push eye in with cotton tip to work against
you; lid fissure widening; weak LR, inhibited MR when looking out; eye comes forward, MR pulls in; slow
saccades very important; restriction—caused by floor fracture, leashes, fat adherence; in small children,
identify whether eye can move fast with doll’s head maneuver or OKN stimulus; paresis—caused by lost
muscle, stretched scar, cranial nerve palsies
|
| Case: paresis—right eye cannot generate adduction saccade; MR destroyed during sinus surgery; patient
with brain tumor cannot look out; restriction to abduction on forced ductions
|
| Treatment for 6th nerve palsy: wait 6 mo for recovery; if LR functioning well with good abduction saccade,
perform recession-resection procedure or bilateral MR resection; if poor LR function, perform transposition
surgery; can use botulinum toxin type A to paralyze MR (to match LR); Hummelsheim (split tendon
transfer)—preserves vertical rectus anterior ciliary vessels; Foster modification (modified Hummelsheim)
secures muscle further back to lateral; Jensen procedure; transfer superior rectus (SR) to LR muscle and inferior
rectus (IR) to LR muscle; put forces laterally; transposition surgery weakens MR and provides lateral
forces
|
| Duane’s syndrome: looks like 6th nerve palsy with lid fissure widening on abduction and narrowing on
adduction; 6th cranial nerve does not develop; 3rd cranial nerve innervates LR (inappropriate) and MR
(appropriate) muscles; get co-contraction and lid fissure narrowing; type 1—no abducens nerve; good adduction,
poor abduction, ET; type 3—equal innervation of LR and MR; eyes do not move in or out;
straight eyes or XT; type 2—does not exist (according to speaker); full abduction; presently called ET
Duane’s, XT Duane’s, or no face turn; face turn indication for surgery; do not operate if no face turn;
take eye with limited ductions and move to primary position; type 3 Duane’s with lots of co-contraction
has upshoot; LR slips up and pulls eye up; either leash effect of LR or abnormal innervation of IO
|
| Cases: 1) left hypotropia; negative head tilt test; could be double elevator palsy (elevation deficit syndrome);
computed tomography (CT) showed orbital hemangioma that caused eye to go down; improved
with corticosteroid injection; strabismus not always related to muscle problems; 2) child seeing double
(red flag); acquired strabismus; right eye not elevating enough; eyes straight in primary position; pupils
normal; neurologically normal; acquired strabismus, incomitant; required CT, which showed hypothalamic
glioma; 3) child 7 yr of age with small angle, incomitant; acquired double vision; stuttering; Arnold-Chiari
malformation; 4) longstanding left hypertropia; limited elevation of right eye since birth;
worse in abduction, better in adduction; diagnosis of double elevator (SR) palsy; 70% of double elevator
palsies actually restrictions; tightened IR muscle; surgery to recess IR; patient does well; truly paretic
with inability to generate upgaze saccade requires transposition procedure
|
Educational Objectives
| The purpose of this program is to provide the listener with information on strabismus. After hearing and
assimilating this program, the clinician will be better able to:
|
 | 1. Describe the strategies for managing intermittent exotropia.
|
| 2. List the criteria for treating accommodative esotropia (ET) with surgery.
|
| 3. Review the presentations of congenital ET.
|
| 4. Discuss the etiology of complex strabismus.
|
| 5. Understand the differences between 6th nerve palsy and Duane’s syndrome.
|
Discussed on This Program
Botulinum toxin type A [Botox, Botox Cosmetic, Dysport]
Suggested Reading
Astle WF et al: Congenital absence of the inferior rectus muscle--diagnosis and management. JAAPOS
7:339, 2003; Bagheri A et al: The effect of bilateral horizontal rectus recession on visual acuity, ocular deviation
or head posture in patients with nystagmus. JAAPOS 9:433, 2005; Bucci MP et al: Latency of saccades,
vergence, and combined movements in children with early onset convergent or divergent
strabismus. Vision Res 46:1384, 2006; Burdon KP et al: Investigation of albinism genes in congenital esotropia.
Mol Vis 16:710, 2003; Chia A et al: Surgical experiences with two-muscle surgery for the treatment
of intermittent exotropia. JAAPOS 10:206, 2006; Chua B et al: Management of Duane retraction
syndrome. J Pediatr Ophthalmol Strabismus 42:13, 2005; Dawson EL et al: Does botulinum toxin have a
role in the treatment of secondary strabismus?. Strabismus 13:71, 2005; Demer JL et al: High-resolution
magnetic resonance imaging demonstrates abnormalities of motor nerves and extraocular muscles in patients
with neuropathic strabismus. JAAPOS 10:135, 2006; Engle EC: The genetic basis of complex strabismus.
Pediatr Res 59:343, 2006; Figueira EC, Hing S: Intermittent exotropia: comparison of treatments.
Clin Experiment Ophthalmo. 34:245, 2006; Gharabaghi D et al: Comparison of results of MR muscle recession
using augmentation, Faden procedure, and slanted recession in the treatment of high accommodative
convergence/accommodation ratio esotropia. J Pediatr Ophthalmol Strabismus 43:91, 2006; Hasbe S et al:
Accuracy of accommodation in heterophoric patients: testing an interaction model in a large clinical sample.
Ophthalmic Physiol Opt 25:582, 2005; Keskinbora KH et al: Long-term results of bilateral MR recession
for congenital esotropia. J Pediatr Ophthalmol Strabismus 41:351, 2004; Kim SH et al: Ultrastructural
study of extraocular muscle tendon axonal profiles in infantile and intermittent exotropia. Acta Ophthalmol
Scand 84:182, 2006; Kitzmann AS et al: Short-term motor and sensory outcomes in acquired nonaccommodative
esotropia of childhood. Strabismus 13:109, 2005; Koc F et al: Resolution in partially accomodative
esotropia during occlusion treatment for amblyopia. Eye 20:325, 2006; Lambert SR, Lynn MJ:
Longitudinal changes in the spherical equivalent refractive error of children with accommodative esotropia.
Br J Ophthalmol 90:357, 2006; Ludwig IH et al: Long-term study of accommodative esotropia. JAAPOS
9:522, 2005; Mets M et al: Management of high accommodative convergence/accommodation ratio
esotropia. J Pediatr Ophthalmol Strabismus 43:8, 2006; Phillips PH, et al: Intermittent exotropia increasing
with near fixation: a "soft" sign of neurological disease. Br J Ophthalmo. 89:1120, 2005; Romanchuk KG
et al: The natural history of surgically untreated intermittent exotropia-looking into the distant future. JAAPOS
10:225, 2006; Rubin SE: Bringing the management of accommodative esotropia into sharp focus. Am
J Ophthalmol 141:914, 2006; Ruiz MF et al: Surgery and botulinum toxin in congenital esotropia. Can J
Ophthalmol 39:639, 2004; Sa HS et al: Extraocular muscle imaging in complex strabismus. Ophthalmic
Surg Lasers Imaging 36:487, 2005; Simonsz HJ et al: Final report of the early vs. late infantile strabismus
surgery study (ELISSS), a controlled, prospective, multicenter study. Strabismus 13:169, 2005; Somer D et
al: The accommodative element in accommodative esotropia. Am J Ophthalmol 141:819, 2006.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any
significant financial relationship with the manufacturer or provider of any commercial product or service
discussed. For this issue, Dr. Wright reported nothing to disclose.
Dr. Wright addressed the Comprehensive Ophthalmology Review Course, held March 10-12, 2006, in Los Angeles,
CA, and sponsored by the Jules Stein Eye Institute and the Doheny Eye Institute. The Audio-Digest Foundation
thanks Dr. Wright and the sponsors for their cooperation in the production of this program.
|
