This statement summarizes the U.S. Preventive Services Task Force (USPSTF) recommendation on screening for visual impairment in children younger than five years and the supporting evidence and updates the 1996 recommendations contained in the Guide to Clinical Preventive Services, second edition.¹ In 1996, the USPSTF recommended vision screening for amblyopia and strabismus in all children before they enter school (B recommendation).¹ Since then, the USPSTF criteria to rate the strength of the evidence have changed.² Therefore, this recommendation statement has been updated and revised based on the current USPSTF methodology and rating of the strength of the evidence. Explanations of the ratings and of the strength of overall evidence are given in Tables 1 and 2, respectively. The complete information on which this statement is based, including evidence tables and references, is available in the systematic evidence review³ and in the update of the evidence⁴ on this topic, available through the USPSTF Web site (http://www.uspreventiveservicestaskforce.org). The recommendation statement and update of the evidence also are available in print from the Agency for Healthcare Research and Quality Publications Clearinghouse (telephone, 800-358-9295; e-mail, ahrqpubs@ahrq.gov). The recommendation also is posted on the Web site of the National Guideline Clearing-house (http://www.guideline.gov).

This recommendation statement was first published in Ann Fam Med 2004;2:263–6.

Summary of Recommendation

• The USPSTF recommends screening to detect amblyopia, strabismus, and defects in visual acuity in children younger than five years. B recommendation.

The USPSTF found no direct evidence that screening for visual impairment in children leads to improved visual acuity. However, the USPSTF found fair evidence that screening tests have reasonable accuracy in identifying strabismus, amblyopia, and refractive error in children with these conditions; that more intensive screening compared with usual screening leads to improved visual acuity; and that treatment of strabismus and amblyopia can improve visual acuity and reduce long-term amblyopia. The USPSTF found no evidence of harms for screening, judged the potential for harms to be small, and concluded that the benefits of screening are likely to outweigh any potential harms.

Clinical Considerations

• The most common causes of visual impairment in children are amblyopia and its risk factors, and refractive error not associated with amblyopia. Amblyopia refers to reduced visual acuity without a detectable organic lesion of the eye and is usually associated with amblyogenic risk factors that interfere with normal binocular vision, such as strabismus (ocular misalignment), anisometropia (a large difference in refractive power between the eyes), cataract (lens opacity), and ptosis (eyelid drooping). Refractive error not associated with amblyopia principally includes myopia (nearsightedness) and hyperopia (farsightedness); both remain correctable regardless of the age at detection.

• Various tests are used widely in the United States to identify visual defects in children, and the choice of tests is influenced by the child’s age. During the first year of life, strabismus can be assessed by the cover test and the Hirschberg light reflex test. Screening children younger than three years for visual acuity is more challenging than screening older children and typically requires testing by specially trained personnel. Newer automated techniques can be used to test these children. Photoscreening can detect amblyogenic risk factors such as strabismus, significant refractive error, and media opacities; however, photoscreening cannot detect amblyopia.

• Traditional vision testing requires a cooperative, verbal child and cannot be performed reliably until ages three to four years. In children older than three years, stereopsis (the ability of both eyes to function together) can be assessed with the Random Dot E test or Titmus Fly Stereotest; visual acuity can be assessed by tests such as the HOTV chart, Lea symbols, or the tumbling E. Some of these tests have better test characteristics than others.

• Based on a review of current evidence, the USP-STF was unable to determine the optimal screening tests, periodicity of screening, or technical proficiency required of the screening physician. Based on expert opinion, the American Academy of Pediatrics (AAP) recommends the following vision screening be performed at all well-child visits starting in the newborn period to three years: ocular history, vision assessment, external inspection of the eyes and lids, ocular motility assessment, pupil examination, and red reflex examination. For children aged three to five years, the AAP recommends the aforementioned screening in addition to age-appropriate visual acuity measurement (using HOTV or tumbling E tests) and ophthalmoscopy.⁵

• The USPSTF found that early detection and treatment of amblyopia and amblyogenic risk factors can improve visual acuity. These treatments include surgery for strabismus and cataracts; use of glasses, contact lenses, or refractive surgery treatments to correct refractive error; and visual training, patching, or atropine therapy of the nonamblyopic eye to treat amblyopia.

• These recommendations do not address screening for other anatomic or pathologic entities, such as macrocornea, cataracts, retinal abnormalities, or neonatal neuroblastoma, nor do they address newer screening technologies currently under investigation.

Discussion

Visual impairment caused by refractive error, amblyopia, strabismus, and astigmatism is a common condition among young children, affecting 5 to 10 percent of all preschoolers. Amblyopia is present in 1 to 4 percent of pre-school-aged children; an estimated 5 to 7 percent of pre-school-aged children have refractive errors.⁴ Uncorrected amblyopia may harm school performance, ability to learn, and later, adult self-image.⁶ Furthermore, uncorrected amblyopia may be a risk factor for future total blindness. Because visual impairment in children is common and believed to have an early sensitive period when interventions lead to better outcomes, much interest has focused on primary care vision-screening tools for early detection, referral, and treatment.

The USPSTF found no direct evidence that screening for visual impairment, compared with no screening, leads to improved visual acuity. However, the USPSTF found one fair-quality study showing that intense screening by eye professionals (compared with usual screening) decreases the prevalence of amblyopia.⁷ This recent randomized controlled trial in the United Kingdom, the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) trial,⁷ has reported that intensive screening performed six times between ages eight and 37 months by an eye professional (using the cover test, Cardiff Cards, Kay Picture test, and HOTV letters) led to decreased prevalence of amblyopia and improved visual acuity compared with a one-time visual screening at age 37 months (using Kays Picture test and HOTV letters). Any child failing a screening test was referred to the hospital eye service for further testing and treatment. Compared with the group screened once at age 37 months, the intensively screened group had a significantly lower prevalence of severe amblyopia at age 7.5 years (amblyopia B prevalence, 0.6 percent versus 1.8 percent) and a lower prevalence of residual amblyopia after treatment (7.5 percent versus 25 percent).

The USPSTF reviewed the evidence for the accuracy of vision screening tests in children younger than five years. The USPSTF found no evidence evaluating the role of screening for family history or parental concern, or evaluating the accuracy of the clinical examination to detect visual impairments such as cataracts or strabismus. One fair-quality study of children aged three to five years who were screened by public health nurses with annual tests, including Cambridge Crowding Cards, the Hirschberg test, and the Titmus Fly Stereotest, reported an overall sensitivity of 60 to 71 percent and a specificity of 70 to 80 percent.⁸ A good-quality systematic review, which evaluated the accuracy of the Snellen E test or Stycar graded balls and the Titmus Fly Stereotest in children aged three to five years, reported an estimated sensitivity of 9 to 12.5 percent and a specificity of 99 percent.⁹ Three poor-quality studies examined the accuracy of the Medical Technology Incorporated photoscreener in a population of children younger than three years with a high prevalence of visual impairment. Sensitivity ranged from 37 to 88 percent, and specificity ranged from 40 to 88 percent.^10–12 For the Visiscreen in children younger than three years, overall sensitivity and specificity were 85 and 94 percent, respectively.¹³

The USPSTF found fair-quality evidence that early treatment of amblyogenic risk factors, including strabismus, refractive error, and cataracts, prevents amblyopia.^14–17 Indirect evidence for the effectiveness of amblyopia treatment comes from cross-sectional studies that show lower prevalence of visual impairment in screened populations compared with unscreened populations.^18,19 Cohort studies show that among children who have been diagnosed with visual impairment, amblyopia is unlikely to improve without therapy.²⁰ Prospective and retrospective studies report that between approximately 40 and 95 percent of persons with amblyopia have improved visual acuity after treatment.^21–33 Two fair-quality studies of treatment for amblyopia have found that successful outcomes depend on earlier treatment.^24,31 In these studies, treatment efficacy steadily decreased after age three years; by age 12 years, treatment was ineffective. However, there is fair evidence to suggest that a modest delay in treatment does not harm outcomes.³⁴ Because the USPSTF found no studies that followed patients into adulthood, the long-term effectiveness of the interventions for amblyopia is unclear.

The USPSTF found no studies detailing permanent harms resulting from screening or data regarding the harms of false-positive screening. However, potential harms of screening may include labeling and the costs associated with the further evaluation of children with false-positive screening results. Potential harms of interventions include disruption of normal eye development and temporary loss of visual acuity of the nonamblyopic eye, which resolves weeks after completion of therapy.³⁵

There is limited research regarding the performance of vision screening tests in the primary care setting, although there are studies^36,37 underway comparing various screening methods (K. Sunnah, project manager, Project Universal Preschool Vision Screening, personal communication, June 2003). Current studies reviewed by the USPSTF, including the ALSPAC study,⁷ support the effectiveness of intensive screening; however, it is not clear whether the magnitude of benefit observed in the United Kingdom study is generalizable to the U.S. population, to children younger than three years, or to services provided by primary care physicians. It would be helpful if similar studies comparing early, intensive screening to usual visual screening were performed in children younger than five years using screening tests commonly performed in the United States by primary care physicians.

Recommendations of Others

The recommendation of the American Academy of Family Physicians can be accessed athttps://www.aafp.org/x7661.xml. The joint recommendation of the AAP, American Association for Pediatric Ophthalmology and Strabismus, and the American Academy of Ophthalmology can be accessed athttp://aap.org/policy/s0208.html.

The clinical practice guideline of the American Optometric Association can be accessed athttp://www.aoa.org/clincare/pdf/CPG-2.pdf. The recommendation of the Canadian Task Force on the Periodic Health Examination can be accessed athttp://www.ctfphc.org.