Issue 39.17
The human eye is amazing. Much of this world we live in can be enjoyed visually. The colors, shapes, and details we can perceive help us to learn and grow in our environment. As parents watch their baby grow and develop they will see many changes to their infant’s visual behavior.
To understand what an infant sees, one must first understand how our eyes develop. Our eyes begin to form as soon as 22 days into gestation. From there the gradual development of the eyes occur with much of the ocular structures developed by about 20 weeks gestation. Retinal development continues until about 40 weeks gestation. The visual pathways of the brain continue development for several years with a significant portion of vision development occurring in the first few months after birth.
At birth, babies have quite limited vision. As one might expect, actually assessing a nonverbal child’s vision can be challenging. There are tools and techniques that make this possible. Many different techniques for assessing vision have been tried, and based on these tools newborns visual acuity is estimated at a level of 20/400 (Figure 1). By 2 months of age visual acuity is estimated at the level of 20/200 (Figures 2). At 4 months of age visual acuity is estimated at the level of 20/100. Visual development after six months of age is more gradual, and most children can see near the 20/40 level (Figure 3) by 2-3 years of age. Clear, or 20/20, visual acuity (Figures 4) can be achieved by most children entering kindergarten.
Many things can interfere with normal visual development. A fairly common visual problem is something called amblyopia. Amblyopia is the condition where vision has not developed as normal in one or both eyes. There are many causes of amblyopia. The most common form is called anisometropic amblyopia, and it is a condition where the prescription in one eye is significantly different from the prescription in the other eye. Most children who have this do not realize there is a problem because they have always seen this way. As a child grows the brain never develops clear vision in the amblyopic eye. Because treatment of amblyopia is best done while a child is young, screening eye exams are part of a well child check and have also been implemented at many preschools and daycares. Most cases of amblyopia can be simply treated with glasses and/or patching.
A pediatrician or family doctor will screen for any eye abnormalities starting just after birth. As a baby grows and develops he or she will meet many milestones. Just as sitting up and crawling are important milestones, there are also visual milestones along the way such as fixating on objects or tracking. If you or your pediatrician doesn’t feel that your child is meeting these milestones, referral to an eye care provider is warranted. If there is a strong family history of eye problems from a young age it is important that your child be checked early.
Dr. Schliesser is a fellowship trained Pediatric Ophthalmologist specializing in the medical and surgical management of pediatric eye diseases and adult strabismus. He is the only full-time Pediatric Ophthalmologist in Southern Utah and is in practice with the Zion Eye Institute. He lives here in St. George with his wife and five children.