Strabismus

Excerpt

Strabismus is derived from a Greek word that translates to "eyes looking obliquely" and means misaligned eyes. Often, strabismic eyes are referred to as "squinting eyes," "crossed eyes," and "wall eyes." Typically, both eyes fixate equally while focusing on an object with the head held in the primary position. In strabismus or squint, 1 or both eyes deviate inwards or outwards and appear to be in nonalignment towards the direction of the focused object (see Image. Strabismus). It can be due to refractive error, binocular fusion abnormalities, or neuromuscular anomalies of ocular movements. If diagnosed and treated early, strabismus has an excellent prognosis. Treatment is usually by refractive error correction, orthoptic exercises, occlusive patching, topical medications, and extraocular muscle surgery.

Orthophoria is defined as the perfect ocular alignment, even when no stimulus for fusion is present. Orthotropia is defined as the correct direction of the eyes under binocular conditions. Both of these terms describe eyes without any manifest strabismus.

Heterophoria is defined as an ocular deviation kept in control by a fusional mechanism. Heterotropia is defined as the deviation that is present on the corneal reflex test itself. This is the manifest deviation that can be related to underlying amblyopia.

The different deviations can be defined as follows:

1. Eso- This is a convergent strabismus in which the eyeball deviates nasally.

2. Exo- This is a divergent strabismus in which the eyeball deviates temporally.

3. Hyper- This is a vertical strabismus in which the eyeball deviates superiorly.

4. Hypo- This is a vertical strabismus in which the eyeball deviates inferiorly.

5. Incyclo- The eyeball is intorted, and the superior pole of the vertical meridian is rotated nasally.

6. Excyclo- The eyeball is extorted, and the superior pole of the vertical meridian is rotated temporally.

Based on the age of onset of strabismus, it can be defined as infantile when the deviation of eyes has been noticed at or before 6 months of age. Strabismus is defined as acquired if the deviation is noticed after 6 months of age, following a presumed normal ocular alignment.

Further, the strabismus is called comitant if the angle of deviation remains the same in different positions of gaze. It is called incomitant if the deviation varies in size in different positions of gaze.