Amblyopia Therapy Is for Older Children Too

Amblyopia (lazy eye) is characterized by unilateral or bilateral impairment in visual acuity, uncorrected by optical means, without detectable anatomic damage in the eye or visual pathway.¹ A diagnosis of amblyopia must satisfy 3 criteria²:

• The best corrected visual acuity is impaired in 1 or both eyes.
• There is a history of 1 or more amblyopia-inducing conditions that affected the amblyopic eye during the period of visual immaturity.
• There is no organic abnormality of the visual system that could fully account for the impaired visual acuity.

Amblyopia may be classified according to the conditions by which it is typically induced. The forms of amblyopia include the following^1-3:

Strabismic. Amblyopia develops in about 40% of children with strabismus, the most common cause of amblyopia. Esodeviations (turning in of the eye) are more commonly associated with amblyopia than are exodeviations (vertical deviations).

Refractive. In patients with isometropic amblyopia, uncorrected bilateral high ametropia causes bilateral blur. In patients with anisometropic amblyopia, image distortion and unequal visual inputs cause unilateral blur.

Form deprivation. This condition is associated with media opacity, eyelid ptosis, and eyelid hemangioma that obstruct the visual axis.

Iatrogenic. This form is induced by occlusion (patching).

MANAGEMENT

Successful treatment of amblyopia must incorporate 2 key strategies.² The first is to optimize the clarity of the retinal image in the amblyopic eye. This is accomplished by providing a clear visual axis (elimination of any obstacle to vision) and correcting significant refractive error. The second is to intensify the neural stimuli to the visual cortex. This is achieved by limiting the stimulus to the nonamblyopic eye, thereby "forcing" the amblyopic eye to function.

Treatment options include the following^2-4:

• Occlusion, either part-time or full-time.
• Optical degradation with opaque contact lens or graded transparent filters on an eyeglass lens.
• Defocusing (penalization) through the application of atropine 1%, a cycloplegic agent, to the stronger eye.
• Active therapy consists of occluding the stronger eye while exposing the amblyopic eye to visual stimuli.

AN IMPORTANT NEW STUDY

Traditionally, treatment of amblyopia in children older than 9 years was not recommended because experts believed that the visual system was mature by that age. However, a new study from the Pediatric Eye Diseases Investigator Group showed that age should not be a limiting factor in initiating amblyopia therapy.⁵ The study enrolled 507 children, aged 7 to 17 years, with amblyopia. All participants were provided with maximal optical correction, and one group was randomly selected to receive additional treatment (2 to 6 hours per day of prescribed patching combined with near visual activities for all patients, plus atropine sulfate eyedrops for children aged 7 to 12 years). Children who showed improvement in the amblyopic eye of 2 or more lines of vision on a standard eye chart were considered responders.

The researchers found that 53% of children aged 7 to 12 years in the treatment group were responders, compared with only 25% of children of the same age in the optical-correction group. In the 13- to 17-year-olds, 25% of the treatment group and 23% of the optical-correction group were responders. In this age group, 47% of children in the treatment group who had never been treated for amblyopia were responders, compared with only 20% of those in the optical-correction group.

Because it was unclear whether improvement in visual acuity could be sustained once treatment was discontinued, the researchers stopped short of recommending a change in current clinical practice. However, they are conducting a 1-year follow-up study to determine the degree of amblyopia that recurs among responders.

SOCIAL STIGMA OF GLASSES

Wearing glasses may affect children socially. In a recent 1-year study, the authors examined data from 6536 preadolescent children who wore glasses, had manifest strabismus, or had a history of wearing an eye patch.⁶ Psychologists interviewed the children to identify the amount of bullying they were involved in, either as victims or as perpetrators. Results showed that after adjustment for sex, visual impairment, social class, and maternal education, these children were 35% to 37% more likely than other children to be targets of physical or verbal bullying. Consider recommending contact lenses instead of glasses for children who feel especially vulnerable.