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Patient Story

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A 5-month-old infant is brought to your office by her mother. The mother reports that the child has a “lazy eye.” On further inquiry, the mother describes a 1-month history of the child’s eyes turning inward toward the nose. This occurs intermittently and is not noticed by the child’s father. The mother shows several photographs that are inconclusive. The infant’s maternal uncle had strabismus surgery as a child. On examination, the infant protests when either eye is covered, and seems to have an inward deviation of the right eye, more pronounced when looking to the left (Figures 15-1 A,B,C). The patient is able to move the eyes easily in all directions.

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FIGURE 15-1

A. Congenital or infantile esotropia. Demonstrates cross-fixation with left eye preference. B. Infant tolerates right eye blockage. C. Infant upset to have left eye covered. (Used with permission from Paul J. Rychwalski, MD.)

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Introduction

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Strabismus refers to any misalignment of the eyes. It can be further categorized based on the direction of the deviating eye(s): 1) esotropia—the eye turns inward; 2) exotropia—the eye turns outward; 3) hyper- and hypotropia—the eye turns upward or downward respectively; and 4) cyclotropia or torsional—the eye is rotated clockwise or counterclockwise. Further, the terms used to describe strabismus also depend upon the conditions under which it is present (constant or intermittent) and whether it changes with the position of gaze (comitant or incomitant).

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Synonyms

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Squint, lazy-eye, cross-eye, walleye, or crooked eye.

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Epidemiology

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  • There is geographical variation in the prevalence of strabismus.

  • Esotropia is more common in Western populations whereas exotropia is more common in Eastern populations.

  • US population-based studies have found an annual incidence per 100,000 population of 64 in exotropia (corresponding to a prevalence of 1 percent of children aged <11 years), 111 in esotropia (corresponding to a prevalence of 2 percent of children aged <6 years), and 12.9 in hypertropia (corresponding to a prevalence of 0.26 percent of children aged <19 years).

  • In the US, the incidence of esotropia is highest in children younger than 7 years, whereas the incidence of exotropia is highest in children aged 6 to 9 years, and is also high in adolescents and adults with sensory strabismus.

  • The prevalence of strabismus is higher in those with intellectual disabilities (44.1%) compared with the general population. The prevalence in white people is 2 percent to 4 percent, but may be lower in Asian populations.13 Among Hispanic and Latino children, prevalence is:

    • 2 percent at ages six to 11 months.

    • 2.6 percent at ages 36 to 47 months.

    • 2.8 percent at ages 60 to 72 months.

  • Among African-American children, prevalence:

    • 1.1 percent at ages six to 11 months.

    • 1.9 percent at ages 36 to 47 months.

    • 3.9 percent at ages 60 to 72 months.4

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Etiology and Pathophysiology

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Proper alignment of the eyes is guaranteed by a normally functioning sensory and motor ...

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