Children are not simply “small adults” when it comes to eye health. The potential problems unique to the developing visual system of a child can lead to permanent vision loss if not detected and treated appropriately. Problems such as amblyopia (lazy eye) and strabismus (when the eyes don’t look in the same direction at the same time) can be treated effectively prior to age 8; afterwards, it is often too late and vision loss may be permanent.
Unlike other sensory systems, the visual system in humans continues to develop after birth, all the way to age 8-10 years. A newborn sees black and white or shades of grey and has a visual acuity of approximately 20/400. The eyes are often misaligned—appearing to be crossing inward or wandering outward. At 3 months, vision improves to about 20/80 and the eyes start working together, appear straight, and even begin to focus on and track objects.
By 6 months, since vision is approaching adult levels (20/20-20/30) and eye muscle control is improved, the child begins to develop depth perception. Color vision is also improved. Thus, by 8-10 months, the child will be able to focus, follow and grasp at objects presented to them.
It is important to detect problems as early as possible. Thus, parents need to take an active role in monitoring for signs of a problem. At the first signs of inward turning of the eyes (esotropia) or outward turning of the eyes (exotropia), the parents should alert their pediatrician. Also, watch for any delay in tracking of moving objects as discussed above. Most importantly, it is essential to have eye screenings at birth, 6 months and again at 3-4 years of age. These screenings are usually performed by a pediatrician or family physician. Any detection of misaligned eyes (strabismus), sub-par vision in one or both eyes, or any other problem should lead to immediate referral to an eye doctor (ophthalmologist)—preferably a pediatric ophthalmologist.
So what can be detected by these all-important vision screenings? In addition to detecting misaligned eyes (strabismus) such as the esotropia or exotropia mentioned above, the vision screen may detect any of the following:
- Myopia—near-sightedness; objects in the distance are blurry
- Hyperopia—far-sightedness; objects up close are blurry
- Astigmatism—near and far objects are blurry or distorted—like looking into a fun-house mirror
- Anisometropia—one eye has much more myopia, hyperopia or astigmatism than the other eye
- Anatomic abnormality and disease—cataracts, glaucoma, ptosis (droopy lid) and tumors, etc
- Amblyopia—often called “lazy eye”
Amblyopia is defined as decreased vision in an eye that displays normal anatomy due to lack of development of the visual system in the brain. Amblyopia develops between the ages of birth and 8 years. By the same token, it can only be treated BEFORE age 8-10 years. Amblyopia can occur in one or both eyes. It can be caused by any of the conditions mentioned above. It can be treated (prior to age 8-10), most often with glasses and/or patching of the stronger eye. The younger the patient, the faster the amblyopia will improve with treatment. Though there have been reports of amblyopia treatment succeeding in older children up to age 12, in the large majority of cases, the cut-off is more like 8-10.
Ultimately, the purpose of vision screening is to prevent avoidable, permanent vision loss due to amblyopia or disease processes. If any abnormality is detected or even suspected, prompt referral to a pediatric ophthalmologist for treatment and close follow-up is paramount. If parents, pediatricians and ophthalmologists all do their part, then we will lower the rate of amblyopia—the leading cause of vision loss in children in the U.S.—from its current unacceptable rate of approximately 1 in 20 children.