Infant Vision Development
By Janelle J Brown, OD
As spring approaches blanketing everything with green buds, we start thinking about new life. What better time to think about the eye care of infants and toddlers? You’ve probably noticed how large an infant’s eyes appear; even though the front portion of an infant’s eyes are 75% of their adult size, the visual system undergoes much more development to reach adult levels by age 4.
At birth, infants only see in shades of gray with very limited visual detail. As the detail-oriented and color detecting cells in the center vision, the cones, develop, the baby’s vision sharpens and they begin to perceive colors around 3-6 months. Many other advancements occur at a similar age, including development of more accurate eye movements to track moving objects and jump the eyes from one thing to another, the perception of depth/3D, and the ability to increase focus as objects move closer. Until age 1, there is a wide variety of farsightedness, nearsightedness, and astigmatism. These prescriptions go through a normalization process as an infant becomes a toddler. Visual acuity and contrast reach their adult levels around age 4. By this time, children are usually able to identify shapes or letters on our vision charts and are more actively involved with their eye exams.
The American Optometric Association recommends routine exams for children between 6 months to 1 year of age, at age 3, and again prior to entering kindergarten. Given the importance of infant eye exams, the AOA developed the InfantSee program, where babies 6 months to 1 year of age receive a comprehensive eye exam at no cost from participating optometrists.
What everyone wonders is how we can get a baby to tell us which option of letters is clearer: “one or two?”. Luckily, we have modified techniques that don’t rely on a patient’s verbal response, allowing us to determine if the patient has a prescription, if the eyes are well aligned, and if there are any eye health concerns. We estimate vision by observing if an infant prefers to look at a paddle with small details over a gray paddle. We use increasingly detailed paddles until the baby reaches their maximum; this gives us an estimate of visual ability.
Next, we check for conditions that affect the eyes’ ability to work together as a team. We test for strabismus, or an eye that is turned outward or inward when both eyes should be looking straight ahead. Furthermore, we determine if an eye turn has impacted the patient’s best-corrected vision. Amblyopia, or inability of one or both eyes to achieve 20/20 acuity, can be caused by a high prescription, an unequal prescription between the eyes, an eye turn, or a congenital media defect that blocks visual information. These conditions are often treated with glasses, by patching an eye, or with vision therapy in school-aged children.
To check for a glasses prescription in a non-verbal patient, we use a retinoscope. We neutralize this instrument’s light reflection with various powered lenses until the proper prescription is determined. Since children have such strong focusing abilities that can mask some of the prescription, this process is often repeated following dilation to ensure accuracy. Additionally, the dilating drops which enlarge the pupil aid our evaluation of the health of the back of the eyes. Although rare, we check for congenital cataracts, tumors, or retinal bleeding, that could permanently affect vision if not treated promptly.
As a parent, bring any of the following concerns to the attention of your child’s pediatrician and optometrist: a noticeable eye turn, a consistent white reflex noticed in one pupil with flash photos, eye redness and discharge, or tears watering down the cheek. Your optometrist is there to reassure you of what is normal and to assist if any concerns arise. Yes, we can do an accurate eye exam in spite of tears and without a word from your child.