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ETIOLOGY OF SQUINT

The general etiological factors which plays role in the development of strabismus can be discussed as:-

1.    Obstacles in the development of normal BSV and coordination

2.    Role of hereditary

3.    Influence of age on the development of strabismus

4.    Development of squint in a blind eye

Thus malfunction of any of the above factors can be an obstacle to the development of normal BSV and binocular resulting in strabismus

These obstacles can be arranged into three groups namely

1.    Sensory

2.    Motor

3.    Central

4.    Sensory obstacle

They are further classified as:-

1.    Extraneous factors

2.    Dioptric factors

3.    Afferent pathway factors

4.    Extraneous factors

Factors which affect the eye from outside like…

  • Prolonged use of ill fitted or in correct glasses
  • Prolonged patching\covering of one eye
  • Persistent conduct of one eye activity
  • Severe unilateral congenital ptosis
  • Malpractice like child kept in dark for too long
  • Dioptric factors
  • Uncorrected R.E or high R.E
  • Anisometropia
  • Medial opacity
  • Afferent pathway
  • Any obstacle in afferent pathway moving from eye or retina to brain or cortical center- It could be due to any congenital or developmental disease

 

MOTOR OBSTACLES

These factors hinds the maintain of two eyes in correct positional relationship in primary gaze or during different ocular movement

They are classified according to:-

·         Static factor

·         Dynamic factor

Static factor: It is stationary condition under which the anatomy of eye is affected which could be leading to squint they are as follows,

·         Congenital abnormality in size and shape of orbit

·         Displacement in orbit due to trauma hence change in direction of axis

·         Facial asymmetry

·         Abnormal facial structures

·         Presence of abnormal tissue in orbit

·         Inflammatory condition or diseases like vascular diseases, endocrinology disorder, chorioretinitis, optic atrophy etc.,

Dynamic factors: this factors can be again classified under the following:

1.    Neurogenic factor

2.    Myogenic factor

3.    Kinetic factor

 

1). NEUROGENIC FACTOR:-  Any lesion in the efferent pathway at any level hampering the mode of sensation from brain to eye it could be developmental or congenital. 

2). MYOGENIC FACTOR :- Abnormalities of EOM such as faulty insertion, innervations, mild paresis under or over development and muscle slips

3). KINETIC FACTORS :-  Any abnormalities in accommodation and convergence and then AC/A ratio which could be result of uncorrected R.E

 

CENTRAL OBSTRACLS

It could be both sensory or motor first hampering the central system due to cause like lesions, tumours at any level, vascular disorder hence can cause squint.

ROLE OF HERIDITORY

Hereditary plays a role in form of passing to the generation in families the cause hence unusually congenital or due to high R.E which are transmitted genetically.

Influence of age on development of Strabismus

If the squint is present congenital it could be of either type based on the type but usually divergent.

In younger patient or childhood which is the developing age can cause convergent squint

In still older people or where in cause is acquired the defect is usually landed up in the divergent squint all in the interest of maintaining single vision and avoiding diplopia

Development of Squint in Blind Eye

If loss of vision is within few months of life to 5 yrs of age there are equal chances of sensory esotropia or sensory exotropia

If it’s after the childhood the chances are of developing exotropia

If blind eye is since birth the eye lies in anatomical position of the rest or divergent squint.

 

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