Ophthalmology · MU Sofia

81. Concomitant strabismus - types, treatment, prophylaxis* (any new squint - urgent referral, if always ophthalmologist)

Covers the classification of squint into apparent, latent and manifest forms, with the four heterophoria types (esophoria, exophoria, hyperphoria and cyclophoria) and their anatomical and physiological causes. It then describes compensated and decompensated symptoms, the cover, Maddox and synoptophore tests, and treatment options. Concomitant convergent and divergent squints are discussed with their causes, features and examination methods, including the cover tests and the Hirschberg test.

Inside: 4 sections · 6 labelled pictures · 15 flashcards · 8 min

Topic 81 of 91 in the MU Sofia syllabus for Ophthalmology (Medicine, Year 4). The free AceMed note covers it in 4 sections, about 1,167 words (8 min of reading), with 15 flashcards.

In this note

  1. Paralytic and concomitant strabismus Topic 56
  2. Concomitant strabismus
  3. Divergent squint
  4. Examination

Paralytic and concomitant strabismus Topic 56

Normally the visual axis are aligned whether the eyes are in the primary gaze position or none thus the definition is

A misalignment of visual axis of the two eyes

3 main groups exist

  1. 1. Apparent/Pseudostrabismus→ it appears to exist but it actually doesn’t it is due pseudoesotropia in prominent epicanthal folds because the full eye is partially covered. In pseudoextropia (diverging) is due to Hypertelorism which is when there is a large separation between the two eyes
  2. 2. Latent squint (heterophoria) It is a condition where the squint /strabismus only occurs when the function of fusion is removed. A small amount of deviation occurs in every person when fusion is removed→ physiological heterophoria
  3. 3. Manifest squint (heterotopias)

There are 4 types

  1. 1. Esophoria ( tendency to convergence ) which has subtypes where the extent of convergence increases in near distance (convergence excess) , extent of esophoria increases in greater distance (divergence weakness) and the last type is indifferent (nonspecific type )
  2. 2. Exophoria is the tendency to diverge has the same subtype as above
  3. 3. Hyperphoria/hypophoria talks about the tendency for the eye to move upwards/downwards in the absence of fusion
  4. 4. The fourth type is called cyclophoria which talk about the extent of rotation around the anterior posterior axis (like a knob) Incylophoria /excylophoria tendency to turn inwards or outwards

The causes of heterophoria can be grouped into anatomical and physiological causes

Anatomical include: orbital symmetry abnormal interpupillary distance if it is large then exophoria and narrow is associated with esophoria Faulty insertion of extraocular muscles, abnormal innervation or variation in the position of the macula in relation to the axis so the eye has to focus differently than the other to focus the beam on macula.

Physiological factors include age (esophoria more common in young while exophoria is more common in the elderly) Accommodation: hypermetropes or excessive near work which increases accommodation are more like to be esophoric while myopic patients are more little to be exophoric. Convergence: excessive use of convergence may lead to esophoria while lack of usage may lead to exophoria Excess use of one eye may lead to exophoria: microscope use /diamond

Symptoms

It may be asymptomatic called compensated heterophoria and it depends on the reserve neuromuscular power to overcome the imbalance and the individual’s desire of maintaining binocular vision.

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