5. ETIOLOGY
• Exact etiology unknown
• Proposed causes:
Excessive tonic divergence
Anatomical and mechanical factors within the orbit
6. MAGICIAN’S FORCEPS
PHENOMENON
• Abnormal proprioceptive impulses
originating from the dominant eye
as a cause of exodeviation as
concluded by Mitsui
• But unlikely that a mechanism
other than a visually elicited fixation
reflex accounts for the
phenomenon
8. 2. CLASSIFICATION ON THE BASIS OF
UNDERLYING FUSIONAL RESERVE
1.Exophoria : XP
2.Intermittent exotropia : X(T)
3.Manifest exotropia : XT
9. PRIMARY EXODEVIATIONS
CLINICAL CHARACTERISTICS
• Latent or intermittent form ↑
• Prevalence less than esodeviations
• Age of onset of the majority is shortly after birth
• Genuine “congenital” exotropia : poor prognosis
11. SIGNS AND SYMPTOMS
• EXOPHORIA:
Eyestrain
Headache
Blurring of vision
Difficulties with prolonged periods of reading
Diplopia
• CHILDREN WITH INTERMITTENT OR CONSTANT
EXOTROPIA:
Less frequently symptomatic
• ADULTS WITH INTERMITTENT EXOTROPIA:
Commonly symptomatic
12. PHOTOPHOBIA
• Common in intermittent exodeviations
Child is outdoors & looking at infinity
No stimulus for convergence
Bright sunlight dazzles the retinas
Disruption of fusion
Deviation becomes manifest
Diplopia and confusion
Child closes one eye
13. MICROPSIA
• Less well known symptom
• Occurs when patient uses accomodative convergence to
control exodeviation at distance
14. SPECIAL TESTS : POST OCCLUSION
TEST OF SCOBEE-BURAIN
DIVERGENCE
EXCESS
NEAR
DEVIATION
AFTER
UNILATERAL
OCCLUSION
TRUE LITTLE
INFULENCE
SIMULATED INCREASE
15. SPECIAL TESTS : +3.00D SPHERICAL
LENS TEST
• +3.00D spherical lenses suspend accommodation and
thus accommodative convergence
EXOTROPIA NEAR DEVIATION USING
+3.00D LENS
LOW AC/A RATIO LITTLE INFLUENCE
HIGH AC/A RATIO INCREASE
16. MEASUREMENTS OF THE DEVIATION
• Unless the target used for distance fixation forces patients
to relax accommodation, and with it convergence, true
deviation of the eyes at distance fixation may remain
concealed.
• Therefore, measure angle while patient reads the 6/9 line
on the visual acuity chart
18. THERAPY
• Exophoria without asthenopia : No Rx
• Symptomatic exophoria and intermittent and constant
exodeviations : Usually Surgery
However, nonsurgical measures may be indicated to
create optimal sensory conditions before surgery
19. NONSURGICAL TREATMENT
SPECTACLE CORRECTION :
• Astigmatism and anisometropia : corrected
• Myopia : fully corrected
• Hypermetropia : correction depends upon its degree and
patient age
As a rule, a hypermetropia of less than +2.00DS in
children : do not correct
• Presbyopia : correct any underlying hypermetropia ,
weakest bifocal lens, base in prisms for near vision
20. NONSURGICAL TREATMENT
USE OF MINUS LENSES :
• High AC/A ratio : minus lenses
• Convergence insufficiency pattern : minus lenses
prescribed as lower segment bifocals
• Divergence excess pattern : minus lenses prescribed as
upper segment bifocals
PRISMS :
• Base in prisms
22. SURGICAL TREATMENT
• Manifest exotropia present at or shortly after birth with no
history of intermittency
↓
Surgery performed as soon as reliable and constant
measures can be obtained
• Large angle constant exodeviation in adults
↓
Surgery performed as soon as diagnosis made
• Exophoria with asthenopia
↓
Surgery only of deviation not controlled by prisms
23. • Intermittent exotropia or constant exotropia preceded by a long period
of intermittency
Observation
-Occasional manifest squint
-Asymptomatic
-No progression
No Surgery
-Manifest squint ˃ 50% of waking hours
-Asthenopic symptoms
-Progression
Surgery
24. The most desirable age at which surgery should be performed for
intermittent exodeviations has been a matter of some dispute
Majority advocate delaying surgery until the child has
reached at least 4 years of age.
Rapid functional deterioration of
fusional control inspite of
nonsurgical Rx
Surgery at an
earlier age should
be considered
25. Finally, the size of deviation determines the decision to operate
FUNCTIONAL POINT OF VIEW Atleast 15 prism diopter
COSMETIC POINT OF VIEW Atleast 20-25 prism diopter
26. GOALS OF SURGERY
• For intermittent exotropia, small surgical overcorrection
(10-20 prism diopter) is desirable :
1. Divergent strabismic eyes show a strong tendency to
revert to their former position
2. Postoperative diplopia → fusional vergences → Stabilize
eventual alignment of eyes
• Lesser degrees of overcorrection → recurrence of
exodeviation
• Higher degrees of overcorrection → necessitate further
surgery for consecutive esotropia
27. CHOICE OF PROCEDURE
TRUE DIVERGENCE EXCESS B/L lateral rectus recession
SIMULATED DIVERGENCE EXCESS
OR BASIC EXOTROPIA
U/L recession-resection of lateral and
medial recti of nondominant eye
CONVERGENCE INSUFFICIENCY B/L medial rectus resection
Recession of lateral rectus muscle is more effective in
reducing the deviation at distance fixation than the
deviation at near
28. SURGICALRECESSION OF LATERAL RECTUS MUSCLE
SURGICAL RESECTION OF MEDIAL RECTUS MUSCLE
3-6 mm depending upon the size of deviation
29. MANAGEMENTOF OVERCORRECTIONS:
(CONSECUTIVE ESOTROPIA)
1. Large ovecorrection with gross limitation of ocular
motility
Immediate Surgery
2. Small overcorrection
Comitant Incomitant
Miotics
Plus lenses
Prism
Surgery
Surgery
MANAGEMENT OF UNDERCORRECTIONS:
Usually surgery
30. SECONDARY EXODEVIATIONS
SENSORY EXOTROPIA
• Primary sensory deficit in one eye:
Anisometropia
Cornea opacities
Dense cataract
Aphakia
Optic atrophy
Central macular scars etc
Disruption of fusion
• Correction of the visual deficit if possible
• Surgical correction : cosmetic
34. Duanes’s retraction syndrome type 2 :
• Lateral rectus innervation present on abduction as well as
adduction
• Abduction:
- normal
• Adduction:
-limited
-globe retraction
-narrowing of palpebral aperture
-upshoot or downshoot
INCOMITANT STRABISMUS
MUSCULOFASCIAL INNERVATIONAL ANOMALIES
35. Duanes’s retraction syndrome type 2 :
• Treatment:
- Results of surgery disappointing
- Indication : significant deviation in primary position or
intolerable anomalous head position
- Ipsilateral recession of lateral rectus muscle
36. CONVERGENCE INSUFFICIENCY
• Remote near point of convergence and poor near fusional
vergence amplitudes
• Older child or adult
• Asthenopic symptoms
• Exophoria at near but not exotropia
• D/D convergence insufficiency type of exotropia
• Treatment :
- Correction of refraction
- Orthoptic exercises
- Base out prisms
- If these fail, base in prism reading glasses
- Medial rectus resection : rare cases
37. CONVERGENCE PARALYSIS
• Little if any fusional vergence amplitude
• Usually secondary to intracranial lesion
• Exotropia and diplopia on attempted near fixation only
• Adduction and accomodation are normal
• Distinct from convergence insufficiency:
- Acute onset
- Inability to overcome any base out prism
• Treatment :
- Base in prism at near
- Occlusion of one eye at near
- Eye muscle surgery is contraindicated
