Strabismus and Prisms Demystified
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Transcript of Strabismus and Prisms Demystified
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O B J E C T I V E S
S T R A B I S M U S R E V I E W
M E A S U R I N G S T R A B I S M U S
T R E A T I N G D I P L O P I A
V E R G E N C E & P R I S M S
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BINOCULAR SINGLE VISION
Sensory fusion = two eyes, one image
Images from each eye cortically blended into one
Advantages: Single image Stereo vision Large visual field
Prerequisites Located on corresponding retinal areas Sufficiently similar in size, brightness
and sharpness.
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MOTOR FUSION
Ability to align the eyes for the maintenance of sensory fusion. Convergence Divergence
Vergence
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OBSTACLES TO SENSORY FUSION
Similar images stimulating non-corresponding retinal points
Strabismus = misalignment of the visual axes
Dissimilar images stimulating corresponding retinal points Anisometropia – asymmetric refractive error Aniseikonia – different sized images Visual deprivation: unilateral cataract or other organic disease of the anterior
visual pathway
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STRABISMUS
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ESOTROPIA
Infantile ET Refractive/accommodative ET
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EXOTROPIA
Alternating constant XT Intermittent XT
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IMPLICATIONS
Suppression – brain ignores “wrong” image to avoid double vision (diplopia)
Leads to: Maldevelopment of areas of the brain responsible for binocular vision. Must clear obstacle to fusion early in childhood in order to allow development of
binocular interaction.
Maldevelopment of area of the brain responsible for recognition of visual input from the suppressed eye.
Amblyopia
Visual maturity ~ 10 years old
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IMPLICATIONS
Stereoblindness: binocular vision is necessary for true stereoacutiy
People who lack fusion/binocular vision use visual cues other than stereo vision to recognize depth.
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CONSEQUENCES IN ADULTHOOD
Diplopia – 1 object, 2 separated images Due to acquired strabismus – adult brain cannot easily suppress one image
Confusion – 2 objects, 2 superimposed images Due to acquired strabismus or aniseikonia
Loss of depth perception
Treatment: EOM surgery, prisms, occlusion.
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DETECTION OF STRABISMUS – CORNEAL LIGHT REFLEXES
Temporal reflex, right eye= esotropia
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WHAT TYPE OF STRABISMUS?
Pseudoesotropia
- Wide epicanthal folds
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DETECTION OF STRABISMUS- BRUCKNER TEST
Direct Ophthalmoscope
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PHOTOSCREENERSiScreen
MTI
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DETECTION OF STRABISMUS- COVER TEST
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ALTERNATE COVER TEST
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WHAT IS A PRISM, ANYWAY?
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LENS REFRACTION VS.
“FAR-SIGHTED” “NEAR-SIGHTED”
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VS. PRISM REFRACTION
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PRISM REFRACTION
∆
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PRISM COVER TESTING
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How would you hold a prism over an EXOTROPIC eye?
Base In
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PRISM COVER TESTING
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NEUROLOGIC IMPLICATIONS
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DIPLOPIA
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“GROUND IN” PRISM
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FRESNEL PRESS-ON PRISM
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TREATMENT OF BINOCULAR DIPLOPIA
Left Medial Rectus Disinsertion 10∆ Exotropia
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CONVERGENCE INSUFFICIENCY
• Difficulty maintaining a converged eye position for near fixation.
• Small angle latent or intermittent exodeviation at near only.
• Normal binocular vision
Symptoms: eyestrain, double vision, tearing, fatigue
Strongly associated with reading and similar near activities.
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CONVERGENCE INSUFFICIENCY
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CONVERGENCE INSUFFICIENCY
Prism recession exercises for CI
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THANK YOU!