Transcript STRABISMUS (SQUINT)

Ocular Motility
M.R Besharati MD
Shahid Sadoughi University
Eye Muscles
Left eye
Superior Oblique/Trochlear Muscle
Superior Rectus Muscle
Medial Rectus Muscle
Lateral Rectus Muscle
Inferior Rectus Muscle
Inferior Oblique Muscle
Anatomy Of The EOM’s
What are the actions of
EOM surround each eye:
Medial Rectus
Adduction
Lateral Rectus
Abduction
Superior Rectus
Elevation,
Adduction,
Intorsion
Inferior Rectus
Depression,
Adduction,
Extorsion
Superior Oblique
Intorsion,
Depression,
Abduction
Inferior Oblique
Extorsion
Elevation
Abduction
Anatomy Of The EOM’s
 The two Oblique are Abductors
 The two Recti are Adductors
 The two Superiors are Intorters
 The two Inferiors are Extorters
Anatomy Of The EOM’s
Origin
A common
tendinous ring
(annulus of Zinn)
Anatomy Of The EOM’s
Blood supply
Each muscle is supplied
by two Anterior Ciliary
Arteries except the Lateral
Rectus which is only
supplied by one.
Anatomy Of The EOM’s
Nerve supply
Third: LPS, MR, IR,
SR, IO
Fourth: SO
Sixth: LR
Ocular motility
CN III
CN III
CN III
CN IV
CN VI
CN III
Eye movement
Three directions of eye movement
 Vertically
 Upward  SR & IO
 Downward  IR & SO
 Horizontally
 Abduction  LR
 Adduction  MR
 Torsionally
 Intorsion (rotate nasally)  SO
 Extorsion (rotate temporally)  IO
Ocular motility
 Agonist Muscles: Receive
equal innervation to ensure
coordinated eye movements
 Agonist/Antagonist Pairs (within
each eye)
Receive reciprocal innervation
Amblyopia: History
 “When the doctor
sees nothing and
the patient sees
nothing, the
diagnosis is
amblyopia.”
What’s Amblyopia?
 Sometimes called “lazy
eye”: characterized by:
 Reduced visual acuity in an
otherwise normal eye.
 Onset early in life (typically
before age 6)
 Associated with a history of
abnormal binocular visual
experience.
Amblyopia
 Unilateral or less commonly,
bilateral reduction of best
corrected visual acuity that
can not be attributed directly
to the effect of any structural
abnormality of the eye or the
posterior visual pathway.
Defect of central vision
Amblyopia screening
Prevalence: 2%-4% .
Commonly unilateral
Nearly all amblyopic visual loss
is preventable or reversible with
timely detection and appropriate
intervention.
Children with amblyopia or at
risk for amblyopia should be
identified at a young age when
the prognosis for successful
treatment is best.
Role of screening is important
Amblyopia: Definition
 Uncorrectable, decreased
vision in an otherwise
structurally normal eye

definition includes an
operated eye made
“structurally normal” by
surgery (e.g. post cataract
surgery)
 May be unilateral (most
common) or bilateral
Associated (causative) Conditions:
 Amblyopia is generally
accompanied by:
 strabismus,
 Anisometropia
 Isoametropia
 form deprivation
 Occlusive
Strabismus refers to an eye-turn.
 normal
F
esotropia
F
F
F
Anisometropic Amblyopia
e.g., one eye in focus
(emmetropic)
and the other out of focus
(e.g. hyperopic)
Amblyopia usually seen
with hyperopic anisometropia
Monocular Form Deprivation
e.g., cataract.
Amblyopia
Functional reduction in visual acuity of an eye caused by
disuse/misuse during the critical period of visual development
•Strabismic Amblyopia – results from abnormal binocular interaction
•The visual cortex suppresses the image from one eye
•Long term suppression results in loss of vision
Amblyopia
Amblyopia is the unilateral or
bilateral decrease of Vision
caused by form vision
deprivation and/or
abnormal binocular interaction
for which there is no
obvious cause found by
physical examination of the
eye.
Can become irreversible
if not treated before
age 6 to 10 years
Management
 First address vision impairment caused by
amblyopia
 Prescription of glasses to correct refractive
errors
 Occlusion therapy
 Alignment
 Medical




Glasses with/without prisms
Patching
Visual training exercises
Surgical
Occlusion Therapy
 Patching the eye with the
better vision
 Full or part-time
 Dependant on
age/cause/severity
 Forces use of amblyopic
eye
 Improvement of V.A
Why We Treat
1- Restore Stereopsis
2- Prevent Amblyopia
3- Prevent Confusion and Diplopia
4- Appearance
Strabismus measurment
Hirschberg Test
•Used as an initial screen for strabismus
•How it works:
•Stand several feet in front of child with penlight
shining at eyes
•Light reflection will be at the same point in each eye
Normal
Exotropia
Esotropia
Cover Test
 Child fixes on target (near or far)
 Examiner covers one eye while observing the
opposite eye for movement
 No movement = normal ocular alignment
 Uncovered eye shifts to re-fixate on object = Manifest
strabismus

Indicates that the covered eye was the fixating eye
Cover-Uncover Test
•Used to detect latent strabismus
•Child fixes on object (near or far)
•A cover is placed over one eye for a few seconds
then rapidly removed
•The eye under the cover is observed for movement
Cover – Uncover test
Orthophoria, normal
No complaints, asymptomatic
Cover – Uncover test
Esophoria, abnormal, common
Only seen when eye is covered
Often asymptomatic, no complaints
Cover – Uncover test
Exophoria, abnormal, common
Only seen when eye is covered
Often asymptomatic, no complaints.
Alternate cover test
 Remember to allow the pt time to fixate on
the target, give them a minute.
 Then quickly cover the other eye to prevent
the pt from regaining fusion.
 But do not go back and forth quickly because
the pt will not have time to refixate.
Alternate Cover test
Exotropia, intermittent
May be visible with or without
alternate cover
May have intermittent diplopia,
especially when tired or sick
Alternate Cover test
Exotropia, Constant
May be visible with or without
alternate cover
May or may not have constant
diplopia
Cover Uncover test
Left Exotropia, Constant
May be visible with or without
alternate cover
Right eye preference
Cover Uncover test
Left Exotropia, Constant
May be visible with or without
alternate cover
Right eye preference
Normal Convergence
Convergence Insufficiency
How much to operate…
Alternate Cover test with Prism
Exotropia, Constant
Use prism to quantitate the
deviation.
Change prism power until
movement is neutralized.
Use this number to plan surgery
Why We Treat
The main types of Amblyopia are:
1. Strabismic amblyopia results from abnormal
binocular interaction where there is continued
monocular suppression of the deviating eye. It is
Characterized by an impairment of vision which is
present even when the eye is forced to fixate.
Why We Treat
2. Anisometropic amblyopia is
caused by a difference in
refractive error. It results from
abnormal binocular interaction
from the superimposition of a
focused and unfocused image or
from the superimposition of large
and small images from
aniseikonia.
3. Deprivation Amblyopia is caused
from form vision deprivation of
one eye.
Why We Treat
- Confusion and Diplopia
DEFINITIONS
1. Visual axis is a line that passes through the point of fixation and the
fovea. The normal visual axes intersect at the point of fixation.
2. Strabismus is a misalignment of the visual axes which, initially, results in
confusion and diplopia.
4. Diplopia is the simultaneous appreciation of two images of one object. it
results from a failure to maintain binocular vision.