Etiology of Heterophoriaand Heterotropia

Tukezban Huseynova, MDSpecialist in Strabismus and Refractive

Cornea,Briz-L Eye Clinic, Baku, Azerbaijan

Tukezban@gmail.com

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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