Strabismus, Amblyopia

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Strabismus, Amblyopia Leukocoria

• Dr. Hessah Alodan,
• Pediatric Opthalmology Dept, KAUH

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Why Two Eyes ?
You can demonstrate to a patient the difference
in their field or their child's field with one
eye compared to two. With two eyes you can also
demonstrate the peripheral field and the central
fusion.
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Why Two Eyes ?
Left Eye Monocular  
Right Eye Monocular  
Binocular  
Total binocular field is nearly 170
degrees (varies according to configuration of
orbits)
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Why Two Eyes ?
Two Pencils Test
The same person with one eye closed or with
manifest strabismus or no stereopsis will miss
the examiner's pencil initially and place it
correctly only after the second or third try.
With both eyes open the patient who uses both
eyes producing stereopsis can put his pencil
accurately on the examiner's pencil if stereopsis
is present
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• Visual Axis
• Imaginary line between fovea and the object
• Binocular Vision
• If the visual axises from both eyes intersect at
  the object, binocular vision occurs

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• Sensory Fusion
• Supper imposed images from each corresponding
  retinal area in binocular cells at the level of
  the occipital cortex
• Same images
• Similar in size
• Similar in clarity
• Motor Fusion
• Ability to physically move the eyes so that they
  are pointing in the same direction allowing the
  corresponding areas of the retina in each eye to
  be pointing at the object of regard

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• Visual Axes Misalignment lead to
• Confusion
• Superimposition of the two different images
  stimulating corresponding retinal points
• Diplopia
• One object stimulating two none corresponding
  retinal points

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• Compensatory mechanism to misalignment of VA
• Suppression
• Subconscious active neglect of one eye input that
  occurs only when both eyes are open
• Amblyopia

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Action of extraocular muscles
Muscle Action
All obliques Abduct
Horizontal Recti Adduct 
All superior muscles  Intort
 All inferior muscles  Extort
Action Muscles
    Dextroelevation  OD Superior RectusOS Inferior Oblique
  Dextrodepression OD Inferior Rectus   OS Superior Oblique
    Levoelevation OD Inferior Oblique OS Superior Rectus
    Levodepression OD Superior Oblique OS Inferior Rectus
       Right gaze OD Lateral Rectus OS Medial Rectus
        Left gaze OD Medial Rectus OS Lateral Rectus


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What is Strabismus ?
Ocular misalignment due to abnormality in
binocular vision or anomalies in neuromuscular
control of ocular motility
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• Classification of Strabismus
• According to fusion status
• Phoria
• Latent tendency of the eye to deviate and
  controlled by fusional mechanism
• Intermittent Phoria
• Fusion control is present part of the time
• Tropia
• Manifest misalignment of the eye all the time

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• Classification of Strabismus
• According to fixation
• Alternating
• Spontaneous alternation of fixation from one eye
  to the other
• Monocular
• Preference of fixation with one eye

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• Classification of Strabismus
• According to type of deviation
• Horizontal
• Esodeviation
• Exodeviation
• Vertical
• Hyperdeviation
• Hypodeviation
• Torsional
• Incyclodeviation
• Excyclodeviation
• Combined

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• Classification of Strabismus
• According to age of onset
• Congenital
• Acquired

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• Classification of Strabismus
• According to variation of the deviation with gaze
  position or fixing eye
• Comitant
• Same deviation in different direction of gaze
• Incomitant
• Variable deviation in different direction of gaze
  usually in paralytic or restrictive type of
  strabismus

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• Examination
• History
• Inspection
• Assessment of monocular eye function
• Visual acuity
• Preverbal children
• CSM
• OKN
• Preferential looking
• Visual evoked potential

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• Examination
• Assessment of monocular eye function
• Visual acuity
• Verbal children
• Symbol tests
• Single illiterate E
• Allen pictures
• H O T V letters

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• Examination
• Assessment of binocular eye function
• Hirschberg test
• Krimskis test
• Cover test
• Alternate cover test
• Prism cover test

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• Examination
• Fundoscopy
• Cycloplegic refraction
• Tropicamide
• Cyclopentolate
• Atropin

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• Type of Strabismus
• Esotropia
• Pseudoesotopia
• Infantile esotropia
• Accommodative esotropia
• Partially accommodative esotropia

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• Pseudoesotropia
• Occur in patients with flat broad nasal bridge
  and prominent epicanthal fold
• Gradually disappear with age
• Hirschberg test differentiate it from true
  esotropia

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• Infantile Esotropia
• Common comitant esotropia occur before six month
  of age
• Deviation is often large more than 40 prism
  diopter
• Frequently associated with nystagmus and inferior
  oblique over action
• Treatment
• Correction of refractive error
• Treat amblyopia
• Surgical correction of strabismus

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• Accommodative Esotropia
• Occur around 2 ½ years of age
• Start as intermittent then become constant
• High hypermetropia
• Treatment
• Full cycloplegic correction
• Treat amblyopia

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• Partially Accommodative Esotropia
• Improve partially with glasses
• Treatment
• Full cycloplegic correction
• Treat amblyopia
• Surgical correction of strabismus

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• Type of Strabismus
• Exotropia
• Intermittent exotropia
• Constant exotropia
• Sensory exotropia

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• Intermittent exotropia
• Onset of deviation within the first year of age
• Closing one eye in bright light
• Usually not associated with any refractive error
• Usually not associated with amblyopia
• Treatment
• Correction of any refractive error
• Surgical correction of strabismus

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• Constant exotropia
• Maybe present at birth or maybe progress from
  intermittent exotropia
• Treatment
• Correction of any refractive error
• Correction of amblyopia
• Surgical correction of strabismus

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• Sensory exotropia
• Constant exotropia that occur following loss of
  vision in one eye e.g trauma
• Treatment
• Correction of any organic lesion of the eye
• Correction of amblyopia
• Surgical correction of strabismus

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• Types of Strabismus
• Paralytic strabismus
• 6th nerve palsy
• 4th nerve palsy
• 3rd nerve palsy

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• 6th Nerve Palsy
• Incomitant esotropia
• Limitation of abduction
• Abnormal head position

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• 4th Nerve Palsy
• Congenital or acquired
• Hypertropia of the affected eye with
  excyclotropia
• Abnormal head position

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• 3rd Nerve Palsy
• Congenital or acquired
• Exotropia with Hypotropia of the affected eye
• In children caused by trauma, inflammation, post
  viral and tumor
• In adult caused by aneurysm, diabetes, neuritis,
  trauma, infection and tumor

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• Special Types of Strabismus
• Duane strabismus
• Brown syndrome
• Thyroid opthalmopathy

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• Duane Syndrome
• Limitation of abduction
• Mild limitation of adduction
• Retraction of the globe and narrowing of the
  palpebral fissure on adduction
• Upshoot or downshoot on adduction
• Pathology faulty innervation of the lateral
  rectus muscle by fibers from medial rectus
  leading to co-contraction of the medial rectus
  and lateral rectus muscles

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• Brown Syndrome
• Limitation of elevation on adduction
• Restriction of the sheath of the superior oblique
  tendon
• Treatment needed in abnormal head position or
  vertical deviation in primary position

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• Thyroid Ophthalmopathy
• Restrictive myopathy commonly involving inferior
  rectus, medial rectus and superior rectus
• Patients presents with hypotropia, esotropia or
  both

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• Surgery of Extraocular Muscle
• Recession weakening procedure where the muscle
  disinserted and sutured posterior to its normal
  insertion

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• Surgery of Extraocular Muscle
• Resection strengthening procedure where part of
  themuscle resected and sutured to its normal
  insertion

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• Complication of Extraocular Muscle Surgery
• Perforation of sclera
• Lost or slipped muscle
• Infection
• Anterior segment anesthesia
• Post operative diplopia
• Congectival granuloma and cyst

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Amblyopia
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• What is Amblyopia ?
• Amblyopia refers to a decrease of vision, either
  unilaterally or bilaterally, for which no cause
  can be found by physical examination of the eye

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Pathophysiology of Amblyopia amblyopia is
believed to result from disuse from inadequate
foveal or peripheral retinal stimulation and/or
abnormal binocular interaction that causes
different visual input from the foveae
 
 
 
 
Cortical ocular dominance columns representing
amblyopic eye less responsive to stimulus and
show changes microscopically
Lateral geniculate layers subserving amblyopic
eyes atrophic
Afferent pupil response has been reported but not
common
No retinal changes - ERG OK
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• Amblyopia
• Three critical periods of human visual acuity
  development have been determined. During these
  time periods, vision can be affected by the
  various mechanisms to cause or reverse amblyopia.
  These periods are as follows
• The development of visual acuity from the 20/200
  range to 20/20, which occurs from birth to age
  3-5 years.
• The period of the highest risk of deprivation
  amblyopia, from a few months to 7 or 8 years.
• The period during which recovery from amblyopia
  can be obtained, from the time of deprivation up
  to the teenage years or even sometimes the adult
  years

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Amblyopia Diagnosis of amblyopia usually
requires a 2-line difference of visual acuity
between the eyes Crowding phenomenon A common
characteristic of amblyopic eyes is difficulty in
distinguishing optotypes that are close together.
Visual acuity often is better when the patient is
presented with single letters rather than a line
of letters
An amblyopic eye with 20/70 full line vision
may be able to see as well 20/30 viewing a single
optotype
to 20/70
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• Causes of Amblyopia
• Many causes of amblyopia exist the most
  important causes are as follows
• Anisometropia
• Inhibition of the fovea occurs to eliminate the
  abnormal binocular interaction caused by one
  defocused image and one focused image.
• This type of amblyopia is more common in patients
  with anisohypermetropia than anisomyopia. Small
  amounts of hyperopic anisometropia, such as 1-2
  diopters, can induce amblyopia. In myopia, mild
  myopic anisometropia up to -3.00 diopters usually
  does not cause amblyopia.

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Causes of Amblyopia Strabismus The patient
favors fixation strongly with one eye and does
not alternate fixation. This leads to inhibition
of visual input to the retinocortical pathways.
Incidence of amblyopia is greater in esotropic
patients than in exotropic patients
Alternation with alternate suppression avoids
amblyopia
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• Causes of Amblyopia
• Visual deprivation
• Amblyopia results from disuse or understimulation
  of the retina. This condition may be unilateral
  or bilateral. Examples include cataract, corneal
  opacities, ptosis, and surgical lid closure

Deprivation Amblyopia
Bilateral Deprivation Amblyopia
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• Causes of Amblyopia
• Organic
• Structural abnormalities of the retina or the
  optic nerve may be present. Functional amblyopia
  may be superimposed on the organic visual loss

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Causes of Amblyopia Ametropic Amblyopia 
Uncorrected high hyperopia is an example of
this bilateral amblyopia.
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• Treatment
• The clinician must first rule out an organic
  cause and treat any obstacle to vision (eg,
  cataract, occlusion of the eye from other
  etiologies).
• Remove cataracts in the first 2 months of life,
  and aphakic correction must occur quickly
• Treatment of anisometropia and refractive errors
  must occur next
• The next step is forcing the use of the amblyopic
  eye by occlusion therapy

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Leukocoria
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Causes of Leukocoria

• Cataract
• Retinoblastoma
• Toxocariasis
• Coats disease
• ROP
• PHPV
• Retinal detachment
• Coloboma
• Retinal dysplasia
• Norries disease

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cataract

• opacification of the lens.
• Congenital cataracts usually are diagnosed at
  birth.
• If a cataract goes undetected in an infant,
  permanent visual loss may ensue.

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• Unilateral cataracts are usually isolated
  sporadic incidents

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• Bilateral cataracts are often inherited and
  associated with other diseases.
• They require a full metabolic, infectious,
  systemic, and genetic workup.
• The common causes are hypoglycemia, trisomy (eg,
  Down, Edward, and Patau syndromes), myotonic
  dystrophy, infectious diseases
• (eg, toxoplasmosis, rubella, cytomegalovirus,
  and herpes simplex TORCH), and prematurity

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RETINOBLASTOMA

• Retinoblastoma is the most common intraocular
  tumor of childhood.

• CLINICAL
• MANIFESTATIONS
• Leukocoria (60)
• Strabismus (20)
•  
• OTHER- Uveitis, Orbital cellulitis, Hyphaema,
  Heterochromia, Glaucoma, Bupthalmos

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RETINOBLASTOMA
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Retinoblastoma

• The disease is bilateral in approximately 30 of
  cases. The average age at diagnosis is 18 months
  and 90 of patients are diagnosed before the age
  of 3 years. Less than 10 of retinoblastoma
  suffers have a family history of the disorder,
  90 of cases are sporadic. Of the sporadic cases,
  the responsible mutation is in a germ cell in
  25 of cases and in a somatic cell in 75 of
  cases

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GENETICS

• Retinoblastoma gene is a recessive oncogene of
  180,000 kilobases.
• Located chromosome- 13q14
• Knudson two hit hypothesis
• Germinal cells have one defective and one normal
  RB gene.
• A somatic mutation results in loss of the normal
  RB gene and hence retinoblastoma develops
  (somatic mutations occur frequently enough in the
  developing retina, therefore lesions usually
  affect both eyes)
•  
• In addition, the first child of a parent who had
  had a unilateral retinoblastoma has a 4 chance
  of developing the disease

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PATHOLOGY

• Arise in primitive photoreceptor
  cells.Characteristic histology
• Retinoblastomas are composed of poorly
  differentiated neuroblastic cells with scanty
  cytoplasm and prominent basophilic nuclei.
• The tumour proliferates rapidly, with a tendency
  to outgrow its blood supply and undergo
  spontaneous necrosis. Necrotic tumour being
  eosinophilic stain pink.
• Characteristic Flexner-Wintersteiner rosettes
  represent an attempt at retinal differentiation.
  Histologically, a ring of cuboidal cells is seen
  surrounding a central lumen. Cuboidal tumour
  cells with basally oriented nuclei arranged
  around a central lumen.

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Retinoblastoma
Calcification is another feature of
retinoblastomas, usually occurring in necrotic
areas. Calcium stains with HE. It is worth
identifying calcium in suspect eyes by
ultrasound, or CT scan to differentiate
retinoblastomas from other tumours.
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MANAGEMENT

• EMPIRICAL GENETIC COUNSELLING
• ENUCLEATION
• unilateral, poor visual prognosis
• PLAQUE
• 4-12mm /- vitreous seeding
• EXTERNAL BEAM
• gt12mm, multiple foci, only eye
• LASER
• consider- indirect, xenon arc
• cryotherapy if lt2dd in size
• CHEMOTHERAPY, if intracranial extension

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Non-Retinoblastoma Malignancies

• Unfortunately, children who have genetic
  retinoblastoma and survive their primary
  intraocular cancer have a substantially increased
  risk of death from one or more nonretinoblastoma
  malignancies over the course of their lifetimes,
  up to 35 of children who have had a bliateral
  retinoblastoma and external beam radiation
  therapy will develop a second cancer by age 25
  years

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Congenital retinal telangiectasis (Coats' disease)

• Congenital retinal telangiectasis (Coats'
  disease) is an idiopathic retinal vascular
  disorder that usually affects young male patients
  unilaterally in their first or second decade of
  life.. Patients may present with decreased
  vision, as well as strabismus or leukocoria in
  children. The hallmark feature of congenital
  retinal telangiectasis is localized fusiform
  aneurysmal dilations of the retinal vessels
  reminiscent of tiny light bulbs

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Persistent hyperplastic primary vitreous (PHPV)

• Persistent hyperplastic primary vitreous (PHPV)
  is a congenital anomaly in which the primary
  vitreous fails to regress in utero. Highly
  vascular mesenchymal tissue nurtures the
  developing lens during intrauterine life. In
  PHPV, the mesenchymal tissue forms a mass behind
  the lens.

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Persistent hyperplastic primary vitreous (PHPV)

• A gray-yellow retrolental membrane may produce
  leukocoria, with the subsequent suspicion of
  retinoblastoma.
• In PHPV, the globe is white and slightly
  microphthalmic. Patients have no history of
  prematurity or oxygen administration.

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RETINOPATHY OF PREMATURITY (ROP)

• Vasoproliferative retinopathy affecting premature
  infants exposed to high oxygen
• INCIDENCE
• Prematurity (lt32/40)
• Birth weight (30 lt 1000gm affected)
• Oxygen duration
• 90 ROP regresses spontaneously, 5 blindness

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RETINOPATHY OF PREMATURITY (ROP)

• Signs include
• neovascularization,
• fibrous bands
• retinal detachments
• vitreous hemorrhage
• leukocoria

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Retinal detachment in childhood

• Retinal detachment in childhood can be confused
  with retinoblastoma, and vice versa. The
  possibility of an underlying retinoblastoma
  should always be considered when a child presents
  with retinal detachment and vitreous hemorrhage,
  even when a history of trauma is obtained.

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Retinal detachment in childhood

• Risk factors
• Trauma
• Surgery
• vitreous detachment
• high myopia
• retinal breaks or tears
• retinal vascular disease
• history of detachment in the other eye

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Retinal detachment in childhood

• Symptoms
• flashes of light
• floaters
• curtain-like decrease in vision

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COLOBOMA

• Optic Disc Coloboma
• Due to failure of closure of foetal fissure
  inferiorly
• May be isolated disc or associated chorioretinal
  coloboma
• Usually sporadic, some AD
• Can be bilateral
• Visual acuity varies from normal to NPL.