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