Vision contributes a great deal to an infant’s perception of the world. Many parents naturally are concerned about their child’s vision. Fortunately, serious eye conditions and blindness are rare in infants. Babies can, however have eye problems, so an eye checkup is still an important part of well-baby care. This issue of “Eye Facts” describes some eye problems that occur.
How and When Do a Baby’s Eyes Develop?
The eyes begin developing two weeks after conception. Over the next four weeks all of the major eye structures form. During this time the eye is particularly vulnerable to injury. For example, if the mother takes drugs or becomes infected with German measles, the eye can be malformed or damaged. During the last seven months of pregnancy the eye continues to grow and mature, and the nerve that connects the eye to the brain (optic nerve) is formed.
At birth a baby’s eye is about 75 percent of the size of an adult eye. During the first two years of life, the optic nerve, visual function and internal eye structures continue to develop.
What Can a Baby See?
The newborn’s visual acuity (sharpness of vision) is approximately 20/400. This is equivalent to seeing only the big letter “E” on an eye chart. Vision slowly improves to 20/20 by age 2 years. Color vision is present at birth.
Newborns at first don’t pay much attention to the visual world but normally will blink when light shines in their eye. By 6 to 8 weeks of age, infants will fix their gaze on an object and follow its movement.
A baby’s eyes should be well aligned (working as a team) by 4 months of age (see “strabismus” below). As the eyes become aligned, three-dimensional vision develops.
How Are a Baby’s Eyes Examined?
The first eye exam takes place in the newborn nursery. The pediatrician performs a screening eye exam to check for infections or structural problems with the eyes: malformed eyelids, cataracts, glaucoma or other abnormalities. When the baby is 6 months old, the pediatrician should check the baby’s eye alignment and visual fixation (how it focuses its gaze).
Pediatricians can treat simple eye problems such as pinkeye (conjunctivitis). If you or your pediatrician believes your baby has a more serious eye problem, which may require medical or surgical treatment, the infant should be referred to an ophthalmologist. No child is too young for a complete eye exam.
An eye doctor’s examination of a baby is similar to that performed on adults. The doctor evaluates the baby’s medical history, vision, eye muscles and eye structures.
The doctor assesses the baby’s vision by observing the following. Does the infant react to light shone in the eyes? Will the baby look at a face or follow a moving toy? Other, more sophisticated vision tests may be used if needed.
Eye drops are used to temporarily enlarge (dilate) the pupils for closer examination of the eyes. The drops may take 30 to 90 minutes to work. The eye doctor then uses an instrument to test the baby’s eye for a refractive error, such as nearsightedness, farsightedness or astigmatism. Most children are farsighted at birth but usually not to a degree requiring glasses. However, a baby –even a newborn- can wear glasses if needed.
Finally, the eye doctor uses a lighted instrument with a magnifying glass (ophthalmoscope) to look inside the eye.
Which Eye Problems Occur in Infants?
Infections – Some newborns may catch conjunctivitis as they pass through the birth canal. Older babies can get this eye infection through exposure to persons infected with it. Infected eyes appear red and puffy and have a sticky discharge. Antibiotic eye drops may be given as treatment.
Blocked tear ducts – Tears drain from the eye through a duct, leading from the inside corner of the eyelid, and into the nose. Some babies are born with a blocked tear duct, which causes tears to back up and overflow. As these infants are prone to eye infections, antibiotics may need to be prescribed. In most cases, the tear ducts open on their own by 1 year of age. Sometimes massage therapy of the duct may be needed. Occasionally the ophthalmologist must perform a surgical procedure to unblock the tear duct.
Cataracts – Inside the eye is a lens that helps it focus, similar to the lens on a camera. The eye’s lens normally is crystal clear. Rarely, babies are born with a cataract- cloudiness of the lens that keeps light from passing through. Cataracts in infants usually are found by the pediatrician during newborn or well-baby exams. If the cataract is severe, the pupil appears white; surgery may be required to remove the cataract.
Strabismus – Strabismus means that the eyes are misaligned. For instance, one eye may be turned in- esotropia (crossed eye)- or turned out- exotropia (walleye). There are actually many forms of strabismus. Eye alignment is normally unsteady at birth but by 4 months of age the eyes should be straight. Any infant who continues to show an eye misalignment after 4 months of age or a child who later acquires strabismus should have a complete eye exam. Untreated strabismus may lead to amblyopia (see below). It is a myth that kids outgrow strabismus.
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Amblyopia – Amblyopia (commonly called lazy eye) is the medical term for a loss of vision in an apparently healthy eye. This occurs in babies and young children if there is an imbalance between the eyes. In these cases, the child may subconsciously use one eye more often. The other eye will then lose vision due to disuse. An eye imbalance can occur when there is cataract, strabismus, ptosis (droopy eyelid), eye injury or a refractive error that is worse in one eye. Amblyopia usually does not have symptoms and often is discovered at a school vision screening. It is ideally treated by an eye doctor before the child is 6 to 10 years old, or the vision loss will be permanent. Treatment encourages the child to use the lazy eye by wearing glasses, and/or wearing a patch over the “good” eye or instilling an eye drop to the good eye.
Ptosis – In a few children, the muscle that raises the upper eyelid fails to develop properly in one or both eyes. This muscle weakness, which causes the upper eyelid to droop, is called ptosis. When an eyelid droops and covers half the eye, that eye may mistakenly appear smaller than the other. Ptosis sometimes may result in amblyopia. If the ptosis is severe, surgery is required to lift the eyelid.
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Retinopathy of Prematurity – If a baby is born prematurely, the blood vessels in the eye that supply the retina are not fully developed. Sometimes these blood vessels develop abnormally and may damage the inside of the eye. Retinopathy of prematurity can be detected only during an ophthalmic exam, which should be performed in premature babies during the first few weeks of life. If the disease is advanced, the eye can be treated to prevent blindness.
Visual inattention – Sometimes an infant does not begin to pay attention to visual stimuli by 6 to 8 weeks of age, as is normal. This may be due to delayed development of the visual system, common in premature infants and also occurring in some full-term babies. Often the visual system will mature normally with time. However, visual inattention can also be a sign of eye disease and may result in permanent and/or progressive vision loss. A complete eye exam is in order if a full-term, healthy baby appears visually inattentive after 3 months of age.
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