The A-B-Sees of Pediatric Vision Screening 

By Beth N. Healy, OD

Ocular disorders in children can cause lifelong visual impairment unless early detection and prompt treatment are realized. Examples of these disorders include amblyopia with a prevalence of 2 to 4 percent, strabismus or structural abnormalities. Vision screening can improve early detection, yet only about 34 states recommend or require preschool vision screening. This makes primary care vision screenings critical. 

At birth, the visual system, including visual processing of the brain, is immature. Rapid development occurs especially in the first six months of life. Eye alignment should be essentially straight at 2 months. By 2 to 6 months, fixation improves from sporadic to fairly accurate with smoother pursuits. Acuity development continues to roughly age 8 or 9. Clear retinal images with equal image clarity and proper eye alignment are crucial for normal visual development. 

Vision assessment starting at birth is recommended by the American Academy of Pediatrics and the American Association for Pediatric Ophthalmology and Strabismus. Specific guidelines vary by organization, but in general, vision screening is recommended at all well child visits, at birth, 6 months, 3 years, 5 years and every one to two years thereafter. All children who fail vision assessment, have an ocular abnormality or are at high risk of eye problems should be referred to a pediatric ophthalmologist or an eye care specialist trained to treat pediatric patients. High-risk children include:

• Very premature infants.
• Family history of congenital cataract, retinoblastoma or genetic or metabolic diseases.
• Severe developmental delay or neurologic difficulties.
• Systemic disease associated with eye abnormalities.

The following procedures should be performed at each screening:

• Ocular history.
• Vision assessment, age appropriate visual acuity (attempt acuity at age 3).
• External inspection of eyes and lids.
• Ocular motility/alignment assessment (corneal reflex test, cover test and random dot E useful).
• Red reflex test and Brückner test.
• Pupil examination.
• Ophthalmoscopy (attempt at age 3 if child is cooperative).

Ocular history

Pay attention to parents' observations and ask related questions such as if the child seems to see well, has an eye that drifts or crosses or an eye that tends to close. Obtain relevant family history. 

Vision assessment (monocular and binocular)

Age 0-3 years - Evaluate ability to fixate and follow objects binocularly, then monocularly when patient is alert. Poor binocular fix and following after 3 months of age can indicate eye or brain abnormalities. At 6 to 12 months old, alternating occlusion can be helpful in detecting a potential problem. Refer if a strong aversion to covering a certain eye is present.

Older than 3 years - Various acuity tests are available, such as picture tests like LEA symbols (See Figure 1.) or Allen cards, or other tests such as HOTV, tumbling E, and Snellen letters or numbers. Stick-on occluder patches should be used to assure no peeking of the occluded eye, plus many kids like playing pirate. Most testing is performed at 10 feet in a well-lit area. A line of targets is preferable to a single object unless crowding bars (See Figure 2.) are present. For LEA or HOTV, four out of five symbols must be matched or named correctly to pass the line. For Snellen, four out of six must be correct to pass the line. Keep in mind Allen figures and tumbling E can be difficult due to recognition and directionality, respectively. For LEA or HOTV, a card with the four symbols can be given to the child, allowing him/her to point to the symbol that matches the target. Refer if vision in children age 5 and younger is less than 10/20 or 20/40, and refer in children 6 and older if less than 20/30. Also refer if there is a two-line difference between eyes (even if each eye passes, for example 20/25 and 20/40).

Figure 1.

Figure 2.

Acuity measurement should occur as soon as possible, usually by age 3. If poor cooperation prevents a result in a 3-year-old, attempt again in four to six months; for a 4-year-old, attempt again in one month. If unable to obtain results after two attempts or if an abnormality is suspected, refer for further testing. 

External examination

Use a penlight to examine ocular structures. For example, ptosis can signal neurologic disease and may lead to amblyopia by inducing astigmatism or by occluding vision. Refer if there is any structural abnormality. 

Ocular motility/alignment

Strabismus can be a sign of orbital, intraocular or intracranial disease. Corneal light reflex test (symmetrical, center of pupil to slightly nasal normal), cross cover test and random dot E stereo testing (four of five trials passing, 40 cm test distance) can aid in detecting strabismus or muscle imbalance. For cover test, have the child fixate a target at 10 feet. Cover each eye while watching for movement of the uncovered eye. Then, every 1 to 2 seconds, alternate occlusion between eyes, watching for movement of the just uncovered eye. If movement is observed, refer due to possible strabismus. 

Pupils

Normal pupils are equal, round and fairly briskly reactive to light. If asymmetry is present, note pupil sizes. Refer if there is asymmetry of greater than 1 mm or abnormality present.

Red reflex test and Brückner (detect opacities, posterior abnormalities – retinoblastoma)

Examine the reflex of each eye with the direct ophthalmoscope 12 to 18 inches away, and then inspect both eyes simultaneously from 1 meter. A bright, reddish-yellow (light gray in dark brown eyes) appearance is normal. Asymmetry, dark spots, dull white appearance or lack of reflex should be referred. For Brückner, view both eyes together from 1 meter while the child focuses on the ophthalmoscope light. Refer if there is asymmetry in color, brightness or size. 

Vision screening can improve early detection of problems, however, prompt intervention also may be necessary to save a child's vision or life. Of the states that recommend or require preschool vision screening, few require follow-up if the screening is failed. Performing screenings and educating parents regarding the importance of follow-up can be critical in reducing lifelong visual impairment.

Beth N. Healy, OD, is a pediatric optometrist at Children's Hospital of Wisconsin and the Medical College of Wisconsin. She also is a member of Children's Specialty Group.

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