Squint
Dr. monn salah
Extraocular Muscles
Origin
Common tendon at the apex of orbit.
(Annulus tendinious communis of zinn)
Insertion
Action
•
•
•
•
•
•
M.R
L.R
S.R
I.R
S.D
I.O
: Adduction
: Abduction
: Elevation (when eye looks out)
: Depression (when eye looks out)
: Depression (when eye looks in)
: Elevation (when eye looks in)
Nerve Supply
1. Oculomotor (3rd cn) :
All muscles except LR and SO.
2. Abducent : LR
3. Trochlear : SO
Types of Squint
• Apparent vs. True
• Horizontal vs. Vertical
• Uniocular vs. alternating
• Concomitant vs. Non Comcominant
Apparent Squint
Causes:
• Epicanthus
• Abnormal angle alpha
Large positive angle (hypermetropia)
 apparent convergent squint
Negative angle alpha (High myopia)
 apparent divergent squint
• Abnormal IPD
Wide IPD  apparent divergent squint
Small IPD  apparent convergent
squint
Diagnosis:
• Cause is present
• Central corneal reflex
• No ocular movement on cover-uncover
test
Latent Squint
(Heterophoria)
Tendency to ocular deviation due to
muscular imbalance, checked by brain to
maintain binocular vision.
Types:
• Horizontal (Eso or exophoria)
• Vertical (Hyper or Hypophoria)
• Torsional (incyclo or excyclophoria)
Symptoms:
Rule: If fully compensated, no symptoms.
• Eye strain (muscular asthenopia)
( Ocular ache, Burning sensation, Headache,
Lacrimation, Photophobia, Blurring of vision)
• Running of letters due to transient diplopia
• Difficulty to follow a rapidly moving object
• Difficulty to change focus from near to far
objects
• Intermittent diplopia
Diagnosis:
• Cover test
• Maddox rod test
• Maddox wing test
Cover Test
Maddox rod
• It measures heterophorias.
• It dissociates 2 eyes for dist. Fixation
• It consists of fused cylindrical red rods line
perpendicular to axis of rod.
• Patient is asked to locate position of red
line to white spot of light.
• To estimate the degree of squint, place
prisms until red line is in the center of
white spot
Maddox Rod Test
Maddox wing
• Measures heterophorias.
• It dissociates 2 eye for near fixation.
R sees white vertical arrow and red horizontal
arrow.
L sees vertical and horizontal row of numbers
• Patient asked which number, arrow is
pointing.
Maddox Wing Test
Treatment:
• No symptoms, no treatment
• Optical treatment (Prisms)
- Exercising prism:
Aim: Strengthen weak muscle
Direction: Base of prism in the direction of dev.
- Relieving prism:
Aim: To relieve annoying symptoms
Direction: Base of prism in opposite
direction of latent deviation.
Concomitant Squint
Angle of squint is the same in all directions
of gaze.
Clinical picture:
• Ocular deviation (No doplopia)
• Amblyopia
• Eccentric fixation
Investigation:
1.
2.
3.
4.
Measure visual acuity
Retinoscopy
Alternate cover test
Measurement of angle squint
- Corneal reflex method
- Prism cover test
- Perimeter
- Synoptophore
5. Diagnosis of amblyopia
-Vision: No improvement with glasses
- Synoptophore
- Worth four dot test
6. Diagnosis of eccentric fixation
7. Grade of binocular vision (synoptophore)
- Simultaneous perception
- Fusion
- Stereopsis
Treatment:
• Depends upon:
- Age of patient and duration of squint
- Accommodative or non accommodative
- Presence or absence of amblyopia
- Type of fixation (central or eccentric)
- Grade of binocular vision
Aim of treatment:
• To restore binocular vision
• To improve visual acuity
• To restore normal appearance
Lines of treatment:
• Drugs: Atropine or miotics
• Spectacles
• Occlusion therapy
• Orthoptic exercises
• Surgical treatment
Binocular Vision
Grading: 1. Simultaneous perception.
2. Fusion
3. Stereopsis
Advantages:
1. Binocular field is larger than uniocular
2. Stereopsis
3. Better visual activity
4. Any defect in vision or field of one eye is
masked by the other
V-Pattern Deviation
It is a pattern in which horizontal deviation
becomes more esotripoic on down-gaze and
more exotropic on up-gaze.
Cause: I.O over action
S.O Polsy
Tt: Weakening of I.O
(recession or disinsertion)
A-Pattern Deviation
It is a pattern in which horizontal deviation
becomes more esotropic on up-gaze and
more exotropic on down-gaze.
Causes: S.O over action
I.O under action
Paralytic Squint
It is a true manifest deviation of the eye due
to paralysis of one or more of EOM, in which
the deviation differs in different directions of
the gaze.
Clinical Picture
1. Limitation of motility in the
direction of action of paralysed
muscles.
2. Deviation of the eye in opposite
direction to action of paralysed
muscles.
• Angle of squint is not constant
(max. on looking in dir. of action of
affected mus. and min. in opp. direction)
• Secondary angle of deviation is much greater
than primary angle of deviation.
• Primary angle of deviation: angle of squint when
normal eye is fixing .
• Secondary angle: angle of squint when the
paralyzed eye is fixing.
• Excessive impulses reach the paralysed muscles
to contract and according to hering law, equal
impulses reach the contralat. Synergist)  more
deviation
3. Binocular diplopia
• Occurs in direction of action of paralysed
ms. and disappears when one eye is
covered.
• Images fall on non-corresponding points
of the retina resulting in 2 images.
True image: Falls in fovea of normal eye
False image: Falls outside fovea of
paralysed eye.
• Diplopia maybe:
Uncrossed: LR palsy
Crossed : MR palsy
4. False projection
• Due to excessive innervation to move the
paralysed eye.
• Cover normal eye and instruct patient to
point to an object, his finger will be
directed from the object in the direction of
action of the paralysed eye.
5. Compensatory head posture
(to avoid diplopia)
- Face turn
- Chin elevation or depression
- Head tilt
6. Headache, vertigo, dizziness,
uncertain gait, nausea and
vomiting.
Investigations
Diplopia chart:
• Ina dark room, place red glass in front
right eye and green glass in front left eye.
• Move a slit of light in all nine directions,
ask the patient:
- Areas of diplopia
- Where is the red and green image
- Distance between 2 images
- Are the images side by side or higher or
tilted
Hess screen:
Principle: is to dissociate the 2 eyes for
distant fixation with the red and
green filters.
(Hering’s law of equal and simultaneous
Innervation of yoke muscles)
Treatment
• Tt. of the cause
• Surgical Tt. H.
(a)If no recovery within 6 mon. surgery
(b)Strengthening the ms. if is weak (paresis)
(c)If completely paralysed, we operate on
other muscles.
- Weaken the direct antagonist
- Weaken the contralat. Synergist
- Strengthen the contralat. Antagonist
- Ms. transposition
Sixth nerve palsy
e.g. Rt. LR palsy
• Rt. Convergent squint
• Limitation of abduction of rt. Eye
• Angle of squint is large when the patient looks
to the right
• Angle of squint is larger when the rt. Eye
attempts fixation
• Diplopia on looking to rt. side (uncrossed)
• False projection occurs to rt. side
• Face turn to the right
Third nerve palsy
• Ptosis
• Deviation of the eye out.
• Limitation of mov. in direction of involved
muscles
• No diplopia (due to ptosis)
• Dilatation of pupil or loss of accom.