Download - Etiology of heterophoria and heterotropia
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Etiology of Heterophoriaand Heterotropia
Tukezban Huseynova, MDSpecialist in Strabismus and Refractive
Cornea,Briz-L Eye Clinic, Baku, Azerbaijan
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Orthoforia occurs where both visual axes are directed towards the fixation point and do not deviate on dissociation.
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Factors that determine the relative position of the visual axes.
Anatomical factors.
Innervational factors.
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Factors Responsible for the Manifestation of a Deviation
Abnormalities of Fusion Mechanism
Reflexologic Theories
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Heterophoria
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Where heterophoria is presented, both visual axes are directed towards the fixation point but deviate on dissociation.
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Classification.• Esophoria - convergence excess - divergence weakness - non-specific• Exophoria - conveargence weakness - divergence excess - non-specific• Hyperphoria/hypophoria• Alternating hyperphoria/hypophoria• Cyclophoria
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Aetiology.Esophoria
• Anatomical – enophthalmos, narrow IPD, extraocular muscle anomalies• Refractive – suprable hypermetropia, anisometropia• High AC/A ratio• Weak negative fusional reserves
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Aetiology.Exophoria
• Anatomical – exophthalmos, wide IPD, extraocular muscle anomalies• Refractive – acquired myopia, presbyopia, anisometropia• Weak positive fusional reserves• Passage of time
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Aetiology.Hyperphoria/hypophoria
• Refractive – high myopia (heavy eye syndrome)• Weak vertical fusional reserves• Anatomical – displaced globes, abnormal extraocular muscles, ptosis
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Heterotropia
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Heterotropia is a condition in which one or other visual axis is not directed towards the fixation point.
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There are a number of different forms of heterotropia:
• Esotropia• Exotropia • Hypertropia• Hypotropia• Cyclotropia • Dissociated vertical deviation (DVD)• Dissiciated horizontal deviation (DHD)
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Factors Causing the Deviation.
Mechanical factors
Structural anomalies of extraocular muscles
Accommodation and refraction in comitant strabismus
Fixation disparity
Previous eye surgeries or brain surgeries
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Factors Causing the Deviation.
Other Innervational (Neurologic) Factors in Comitant Strabismus.
Paretic elements Anomalies of the brainstem Anomalies of convergence and divergence Vestibular system Anomalies of the visual pathway Brain damage Embryopathy
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Thank You