“Can my baby see?” – Vision screening in infants and children

“Can my baby see?” – Vision screening in infants and children
by Manolette R. Roque, MD, MBA

“Can my baby see? Is his vision normal for his age? How can you tell? How often should I have my baby seen?” These are some of the frequent questions that anxious new parents ask me in clinic. I will attempt to answer them in simple terms in order to provide the readers of BABY magazine enough useful information to guide them with their new role.

It is extremely important to remember that pediatric visual screening uses simple yet powerful techniques to detect ocular disorders at a young age when treatment is most effective. Unbeknownst to many parents, the developing visual system of infants and children can be permanently damaged by an abnormal visual image which may be caused by ocular misalignment (strabismus or squint), obstructed ocular media (lid ptosis, corneal opacity, cataract, and vitreous hemorrhage), high or unequal refractive error (anisometropia), or unsteady visual images (nystagmus). Significant ocular disease may often be missed, especially if only one eye is affected. Sometimes, vision-, as well as, life-threatening (retinoblastoma) disease may present with ocular signs.

When identifying visual abnormalities, it is important to understand the normal visual development. If you know what is normal for a child’s age, it would be easier to detect abnormal visual function. Visual acuity is expressed as a fraction. The top number refers to the distance you stand from the chart, usually 20 feet. The bottom number indicates the distance at which a person with normal eyesight could read the same line you correctly read. The less the bottom number in the visual acuity ratio, the better the acuity; and the greater the bottom number, the worse the acuity. Visual acuity at birth is quite poor, typically 20/1600, due to the immaturity of the central nervous system visual pathways and visual processing areas. Visual acuity improves to 20/100 by four months of age, and theoretically reaches nearly 20/20 by 12 months of age. A cooperative three year old should be able to demonstrate a visual acuity of 20/40, and a five year old 20/30. Many newborns show variable ocular alignment, with 70% showing exotropia (outward turning of eyes) and 30% having straight eyes. Esotropia (inward turning of eyes) is rare. By two or three months of age, most infants would have straight eyes. Misaligned eyes beyond three months of age require ophthalmic evaluation.

On more than one occasion, a general ophthalmologist will confess to seeing a parent distraught over the thought of not being able to improve the vision, despite proper spectacle correction, of his school aged child after having gone through an initial visual test at age ten or above! Abnormal visual development (amblyopia) is due to abnormal visual stimulation by blurred, misaligned, or unsteady visual image(s). It may be classified into several types, namely: (1) deprivation, from cataract, corneal opacity; (2) anisometropic, from unequal refractive error, (3) strabismic, from ocular misalignment, (4) bilateral deprivation, from cataract of both eyes, nystagmus, (5) bilateral ametropic, from high refractive error of both eyes, and (6) occlusion, from excessive patching of the good eye. The treatment of amblyopia is step-wise in fashion. First, the obstruction in light entry is addressed. Ocular media is cleared by cataract surgery, corneal transplantation, etc. Once the media is clear, the image is focused with glasses, contact lenses, or occasionally intraocular lenses. Finally, ocular dominance is corrected by patching or blurring the better seeing eye.

A lot of parents inquire as to when they should bring in their baby for eye examination. We recommend that pediatricians, the front liners (!), screen at birth, six months, three years and five years of age. It is further recommended that children be subjected to an annual screening at school age until secondary school. An effective pediatric vision screening examination involves (1) inspection, (2) visual acuity testing, (3) ocular alignment testing, and (4) fundus red reflex testing. Ophthalmologists may be seen directly for this purpose.

Allow me to give you a brief overview of each of the four distinct components of an effective pediatric vision screening examination. INSPECTION may be performed by the parents even before consultation. It is obtained by the physician as the child is greeted and while the history is taken from the parents. The following findings are determined: asymmetry of corneal size, pupil size or eyelid position, head turn or head tilt, nystagmus, obvious strabismus, tearing, ocular redness, ocular discharge, and abnormal eye structure. VISUAL ACUITY TESTING can be tricky in babies and children. It is initially done binocularly, followed by monocular (patching one eye) testing. The test method depends on the age of the child. In newborns, one looks for a glare response to a bright light stimulus. A three month old baby should fix upon and follow the examiner’s face. A six month old should fix and follow a brightly (red/yellow) colored toy, sometimes attached to a bright light. One can be more ingenious with one year olds by allowing them to reach out for goodies (candy/cereal) placed in one of two outstretched hands. The examiner has to be quick in determining the response of babies at this age. Any asymmetry in response between the two eyes requires repeat testing, sometimes on a different clinic visit, or immediate referral to an ophthalmologist for further testing. Occlusion of one eye may sometimes result in a crying fit, a big red flag for monocular preference. Preferential gaze or use of one eye should also alert the parent or physician of poor vision on one eye. Verbal children (three years or older) are much easier to test quantitatively with games of matching symbols. A lot of pediatric charts are now out in the market for this purpose. Poor results with these standardized tests warrants a comprehensive eye examination with an ophthalmologist. OCULAR ALIGNMENT TESTING may be performed by the corneal light reflex test, cover test, and fundus red reflex test. The parent may initially perform the corneal light reflex test, using a bright light in a dimmed room, by searching for the corneal light reflex in the middle of both pupils. A decentration of the reflex heralds the presence of strabismus. Lateral (temporal) decentration means the eye is turned inward (esotropia), while medial (nasal) decentration means the eye is turned outward (exotropia). Vertical deviations (hypertropia and hypotropia) may also be identified this way. The second and third tests are more difficult procedures requiring skilled examiners. The cover test is the gold standard for diagnosing strabismus. Ophthalmologists use a combination of prisms and covers to check for shifting or refixation of eyes. The fundus red reflex test (Bruckner Test), is a simple yet powerful test to detect unequal refractive error, media opacity, strabismus, corneal abrasions, and foreign bodies. This test is an integral part of newborn examination. The use of eyelid speculums may be needed in order to complete this test.

I hope this summary is clear and concise enough to be of use to our new parents out there! The benefit of early detection of eye disease, through early treatment with improved outcomes, far outweighs the mild hassle of pediatric vision screening. Go see your pediatrician and ophthalmologist today.

MANOLETTE R. ROQUE, MD, MBA
Email: manolette.roque@eyerepublic.com.ph