Visual impairment is common in children younger than age 5
years. Early detection of visual impairment is thought to lead to better outcomes.
New screening technologies, such as photorefractive screening, allow for the
screening of very young children.
To review systematically the literature regarding the
effectiveness of screening for visual impairment in children younger than age 3
years, and in children 3 years through 5 years of age.
We systematically searched MEDLINE® from 1966 through
1999 to identify studies regarding the prevalence of visual impairment, the
effectiveness of treatment, the diagnostic accuracy of the screening tests, and the
consequences of treated and untreated visual impairment. We also conducted
hand-checks of bibliographies and extensive peer review to identify articles not
captured through our main search strategy.
We included prevalence studies if they reflected the
general population and evaluated subjects systematically for those conditions for
which screening could be useful. We retained diagnostic accuracy studies if they
evaluated commercially available tests and reported sensitivity and specificity
results based on evaluation against a criterion standard. We included treatment
outcome studies if they involved children younger than age 5 years and had a
standard measure of visual acuity as an outcome measure. Studies of the consequences
of treated or untreated visual impairment were used if the visual impariment was
present by at least age 5 years.
A single reviewer examined titles and abstracts of articles and excluded those that
clearly did not meet inclusion criteria. This reviewer then examined the full
articles of the remaining studies to determine final eligibility.
The prevalence of visual impairment in children 5 years
of age and younger is between 7% and 8%. Three percent of children have amblyopia.
Few data are available regarding the long-term consequences of untreated
We found no randomized trials of screening. Treating children younger than age years
who have cataracts or strabismus may prevent the development of amblyopia. It is
unclear whether treating young children with refractive errors associated with
amblyopia would prevent the development of amblyopia. Furthermore, a theoretical
risk exists that treating refractive errors in children younger than age 3 years may
interfere with the normal development of the eye.
Indirect evidence supports the effectiveness of treatment for amblyopia and indicates
treatment becomes more difficult with age. The cut-off age at which treatment is no
longer effective depends on many factors, including the cause of the amblyopia. In
general, treatment seems most effective when initiated before the grade-school
years. Treatment for amblyopia may transiently decrease acuity in the nonamblyopic
Treatment of refractive errors not associated with amblyopia is nearly always
successful and does not depend upon the age of the child. As with the treatment of
refractive errors associated with amblyopia, treating children younger than age 3
years in the circumstance may, at least theoretically, interfere with the normal
development of the eye.
Few high-quality data are available regarding the performance of current screening
tests. None of these studies was performed in the primary care practice setting by
usual caregivers. Few data are available about the long-term consequences of visual
impairment in children.
Visual impairment is common in childhood. Although early
intervention is important for the prevention or treatment of visual impairment,
treatment of certain refractive errors in children younger than age 3 years may
interfere with the development of the eye. Few data are available regarding the
performance of screening tests in the primary care practice setting.