Pediatric Vision Screening

Vision assessment is essential for early detection of conditions that may cause vision loss in young children. The American Academy of Pediatrics recommends vision assessment starting at birth and continuing as part of routine health supervision checks. Early identification through screening before age 7 years can reduce certain causes of blindness, such as amblyopia, by up to half. Starting in the newborn period, screening during health supervision checks provides early opportunities to diagnose a variety of vision concerns and should routinely occur in all children through adolescence. Because of challenges obtaining full cooperation from young children and infants, vision screening consists of multiple components, including medical history, physical examination, and tools such as acuity testing and instrument-based screening.Medical history can be helpful in identifying children at risk for vision loss, although many young children or infants will not be able to verbalize their challenges with sight. Special consideration should occur for children with developmental delay, disability, or other medical conditions that have known risk factors for vision problems, including prematurity, cerebral palsy, congenital cytomegalovirus, eyelid hemangiomas, sickle cell disease, Down syndrome, Marfan syndrome, and Sturge-Weber syndrome. Vision screening in the office may be challenging for this group of patients, and referral to a pediatric ophthalmologist is generally needed. Family history is also an important element of vision screening because it is a known risk factor for amblyopia and strabismus. Parent observations and concerns about eye abnormalities always merit further evaluation and play an important role in early detection. Generally, parent concern should trigger a referral to an eye care specialist because not all abnormalities can be detected during screening and primary care examination. Although routine vision screening should occur at regular intervals, additional screening should be undertaken at visits where a vision problem is suspected, and referral to an eye care specialist should be made if screening is abnormal. Vision assessment can occur with both instrument-based and provider-based vision screening tools. Instrument-based vision screening can identify vision problems before a child can developmentally participate in visual acuity testing. American Academy of Pediatrics guidelines suggest that instrument-based screening can be started at age 1 year and used until a child can read an eye chart. Instrument-based screeners evaluate whether a child has certain risk factors for amblyopia, such as high refractive error, anisometropia, astigmatism, and strabismus. An advantage of instrument-based screening in young children is that it is quick to perform, requiring minimal cooperation from the child. Although instrument-based screening is especially helpful in young children, it is not able to measure visual acuity and thus may miss certain causes of vision loss. There are currently 2 types of instrument-based vision screeners: photo screeners and autorefractors. Photo screeners are binocular devices and can estimate ocular alignment, eyelid position, and refractive error. Autorefractors are monocular devices and estimate refractive error. These instrument-based vision screeners are commercially available. Screening should transition to eye charts when a child is developmentally able to participate.Visual acuity testing should be performed in all children starting at age 3 years through adolescence; however, signs of poor visual acuity are notable at much younger ages. Vision screening has been recommended by the US Preventive Services Task Force with grade “B” evidence for ages 3 years and older. Infants younger than 2 months should have equal pupillary reaction and blink in response to bright light. Around 8 weeks of age, fixation and tracking of objects should be seen. Newborns can have intermittent strabismus, which should resolve by 4 months. Children aged 6 months to 2 years can typically fix on and follow an object with both eyes with normal eye alignment. Starting at age 3 years, visual acuity can be measured using an eye chart, measuring each eye individually and then both eyes together. Use of an appropriate optotype chart can affect the accuracy of the visual acuity obtained. Currently, the American Academy of Ophthalmology recommends use of Lea Symbols or HOTV letters to help optimize standardization of charts that minimize cultural bias. Both Lea Symbols and HOTV letters are easier for young children to understand given their symmetry and inability to be reversed. These charts also allow more reserved children to point to the optotypes that they recognize on a card with similar symbols, allowing effective nonverbal responses to testing. Other optotypes, including Allen Figures, tumbling E charts, and Lighthouse symbols, are no longer recommended because they are not standardized, and children of preschool age may not yet have the ability to express the orientation of these optotypes. Referral should take place to ophthalmology for 3-year-old children with vision worse than 20/50 in either eye, 20/40 or worse in either eye at age 4 years, and 20/30 or worse in children after age 5 years. A 2-line difference between eyes at any age warrants a referral.Although visual acuity testing is often thought of as the predominant part of a vision assessment, the physical examination is also essential. In an office visit, the provider should use the red reflex test starting at birth and continuing in all age groups. An ophthalmoscope should be used to view both eyes simultaneously from approximately 2 to 3 ft away. A normal red reflex test occurs with a present, bilateral, equal red reflex. Absent, white, dull, or asymmetrical red reflex warrants urgent referral to pediatric ophthalmology due to concerns for cataracts, retinoblastoma, or other neurologic conditions. Pupil examination should show bilaterally equal pupils in size and reactivity to light. Patients with signs of anisocoria, or different-shaped pupils, should be referred because this may be a sign of a visual system dysfunction such as ocular injury, ocular disease, or an underlying neurologic disorder. External inspection of the eyes in all age groups allows providers to evaluate for structural anomalies such as ptosis, hemangiomas, or port-wine stains, which can be connected to other underlying endocrine (thyroid) or neurologic abnormalities. Eye asymmetry or eye enlargement, especially if accompanied by tearing or photophobia, are reasons for immediate referral for evaluation for possible pediatric glaucoma. Use of the cover-uncover test and the Hirschberg test is helpful to assess for eye misalignment. The cover-uncover test asks a child to fix their eyes on the provider's nose and for the provider to cover 1 eye and subsequently watch the uncovered eye for any exodeviation. Participation in this part of the examination requires a child to be able to follow directions and fix their view, so it is often best performed in children 3 years and older. The Hirschberg test examines central and equal pupillary light reflexes and can be performed starting in the newborn period. If a light reflex is nasal to the pupil, that eye may have exotropia (1 eye deviates outward). If the light reflex is temporal to the pupil, that eye may have esotropia (1 eye deviates inward). Tropia is a physical misalignment of 1 or both eyes, whereas phoria is a misalignment or deviation that is present only when eyes are not looking at the same object. Recognition of this difference is key in understanding the importance of utilization of both the cover-uncover and Hirschberg tests. It can be challenging to differentiate between pseudoesotropia (where eyes appear crossed but are straight), often due to prominent epicanthal folds or flattened nasal bridge, from true strabismus. It is also vital to evaluate ocular motility. Nystagmus or other unusual eye movements in young children warrant further evaluation because this may indicate poor vision or neurologic dysfunction. Parental observation of these eye movements may be the initial presentation of a more complicated strabismus syndrome, such as congenital fourth nerve palsy, Duane syndrome, or Brown syndrome.Children with abnormal findings on examination—visual acuity screening or instrument-based screening—should be referred to an ophthalmologist or other eye specialist with expertise with children for more definitive examination and treatment. Urgent evaluation by an ophthalmologist should be completed in children with an acute change in vision or children who have a suspected traumatic, infectious, or malignant etiology of vision loss. Examples include retinoblastoma, ocular melanoma, traumatic injury to the eye, orbital cellulitis, herpes keratitis, cataract, or glaucoma.Abnormal red reflexes also warrant urgent referrals because they may be an indicator of cataracts in newborn infants or of retinoblastoma in an older child. Identification of visual disorders can allow interventions such as prescription glasses, patching, atropine drops, or, occasionally, surgery. These treatments have been shown to improve visual acuity, and an ophthalmologist or other eye specialist can guide the choice of the appropriate treatment of individual patients. Vision screening is an important part of the health supervision visit and provides opportunities to identify and treat preventable causes of vision loss and provide support to children with visual impairment.Comments: If you have the ability to see, this is, in my opinion, often taken for granted. Vision screening in children helps to optimize this ability. In reading this In Brief, I was reminded of 2 patients. The first was a 5-year-old who presented to our office for her first examination in several years and she had a concerning result on her first visual acuity screening examination. She required glasses for a significant refractive error, and once she started wearing them, she commented how much more beautiful the world was and how many more details she saw. Before this, neither her parents nor she had realized how poor her vision was.The other patient demonstrates an example of how findings from the vision examination can lead to concern for a systemic illness. This patient was 4 months old and had horizontal nystagmus. A more urgent referral was needed because this was caused by septo-optic dysplasia, which in her case led to the discovery of visual impairment and pituitary hypoplasia. She required evaluation and treatment of the pituitary hypoplasia and underwent genetic testing, which was important to family members. Both of these cases reinforce the importance of vision screening throughout the age span of pediatrics.Janet Serwint, MDAssociate Editor, In Brief