Other Causes of Strabismus

Acute strabismus may be brought on by a viral upper respiratory tract infection, which can cause acute cranial nerve VI palsy. With the advent of antibiotics, middle ear infections with associated petrositis and cranial nerve VI palsies are relatively uncommon. Sudden-onset strabismus may also indicate underlying neurologic disease. Another cause is spasm of the near reflex. A hallmark of spasm of convergence is a constricted pupil. Paralytic or mechanical causes of strabismus occur with trauma and Duane's syndrome. In addition, neurologic trauma accounts for paralysis to cranial nerves III, IV, and VI (Fig. 41-24).

The proper corrective treatment for strabismus includes non-surgical treatment, such as patching and glasses, and surgical treatment, when indicated. Eye muscle surgery is performed when nonsurgical methods cannot correct the misalignment, as well as with worsening misalignment, no effect on the deviation or stereopsis, or progressive loss of fusion. Four aspects of strabismus surgery should also be stressed, as follows:

1. The surgery is safe and effective.

2. The eyeball is never removed from the orbit to perform the surgery.

3. More than one procedure may be required to establish alignment.

4. Both eyes may require surgery to correct the strabismus. The goals when treating strabismus include the ability to provide and maintain equal vision in both eyes, enable the eye to work together rather than independently, and improve depth perception, whenever possible.

KEY TREATMENT

Surgical and nonsurgical treatment of strabismus is beneficial to appropriate visual development, reduction of amblyopia, and rehabilitation of sensorimotor function or depth perception (AAO, 2007) (SOR: A).

Right superior rectus

RIGHT EYE

Right Left inferior inferior oblique oblique

LEFT EYE

Right inferior rectus

Figure 41-15 Ocular muscle movement in cardinal fields of gaze.

Right

Left superior superior oblique oblique

Left superior rectus

Right superior rectus

Right Left inferior inferior oblique oblique

Left superior rectus

Figure 41-15 Ocular muscle movement in cardinal fields of gaze.

Right

Left

Left inferior rectus

Left inferior rectus

Table 41-5 Classification of Strabismus

Type

Cases(%)

Age of Onset

Congenital or infantile esotropia

20

Birth to 6 mo

Accommodative esotropia

45-50

6 mo to 7 yr (usually 2 yr)

Nonaccommodative (acquired) esotropia

10

Variable, depending on cause

Exotropia

20

Variable (usually during infancy to 4 yr)

Hypertropia

<5

Variable, depending on cause

Figure 41-16 Clinical esotropia in 12-month-old infant. With the right eye fixing, there is a left esotropia.

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