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Refractive errors in children: to correct or not to correct?
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Practitioners must consider refractive errors in children differently than refractive errors in adults. Treating myopia in infants is usually unnecessary, but children can be corrected with spectacles or contact lenses. While hyperopic children may become less hyperopic as they age, they should be monitored for other potential visual problems.
“We believe that amblyopia is a greater cause of childhood visual disability than probably all other causes combined,” said Bruce Moore, OD, of the New England College of Optometry.
Hyperopia is the most common refractive finding in children. “It appears that while the prevalence of hyperopia of at least 3.5 to 4 D in a 6-month-old is approximately 6% to 8%, the prevalence of accommodative esotropia by 4 years is about 1.5% of the population. Only about 25% of the kids who are significantly hyperopic at 4 months of age stay that way and get into trouble later. So if you treat all of the kids who are significant hyperopes, you are unnecessarily treating 75% of them. It would make sense to assume that there are some other factors that will predict which kids will get in trouble and which kids will undergo emmetropization,” Dr. Moore said.
However, hyperopia is far more likely to be associated with amblyopia than either myopia or emmetropia. “Although many have assumptions about which cases would lead to amblyopia,” he said, “no studies have followed young children to see exactly what conditions are risk factors for the development of amblyopia.”
Risk factors for amblyopia
Until a natural history study of hyperopia development is completed, what assumptions are pediatric optometrists making about treating hyperopia? Paulette P. Schmidt, OD, MS, FAAO, of the Ohio State University College of Optometry said, “For any child older than 1 year of age who has 2 to 2.5 D of hyperopia, I look for any coexisting conditions that suggest this child is at risk for developing amblyopia or strabismus.”
She particularly looks for any unilateral difference in refractive error in either hyperopia or astigmatism. “I really watch the child with asymmetry,” she added.
Additionally, she said, “I’m going to closely monitor any child with more than 2.5 D of hyperopia. If I find anything suggesting an abnormal AC/A ratio, I will watch closely, and I will prescribe diagnostic lenses to see how the prescription affects sensory assessments, such as visual acuity and stereo acuity and parental reports on the child’s interaction in the world.”
She added that she would check the child with the diagnostic prescription at 1 week to 1 month.
Karen Fern, OD, FAAO, associate professor at the University of Houston College of Optometry, also closely monitors the child with apparently significant refractive error for the first 18 months of life when the visual system is developing rapidly. For the infant with more than 2.5 to 3 D of hyperopia with apparently straight eyes and no family history of eye turn or amblyopia, she recommends follow-up in 2 to 4 months, but requires the parent to call immediately if he or she sees any strabismus. She is concerned about interfering with the process of emmetropization.
“We don’t even know for sure how correcting influences emmetropization,” she said. When she does prescribe, she monitors closely to allow for changes in the refractive error as the visual system matures.
Dr. Fern cautions against prescribing half the hyperopia and feels that the lessened amount of blur in a high bilateral hyperope can trigger the visual system to accommodate and result in accommodative esotropia and unilateral amblyopia. She recommends cutting the full prescription about 1 to 2 D, depending upon the magnitude of hyperopia. The mean refractive error is about +1 D by 12 months of age. Again, she follows this closely so she can reduce the plus if the child becomes less hyperopic. The child with an accommodative esotropia gets the full prescription, if necessary, to eliminate the strabismus.
Astigmatism more prevalent
Astigmatism in amounts that would be clinically significant in adults is more prevalent in infants and young children. Dr. Schmidt said that the literature suggests that about 45% of children between 6 months and 2½ years of age will have 1 D or more of astigmatism, but this is bilateral, transient and drops to adult levels of 8% to 10% by 2½ to 3 years of age.
During this time, visual acuity does not seem to be affected when the astigmatism is bilateral. Dr. Schmidt said that if visual acuity is good and stereo acuity is developing normally, there is no need to intervene. If the astigmatism is unilateral, she checks for a lag in visual or stereo acuity development as well as a problem with the AC/A ratio. If the child is 2½ to 3 years of age, she will consider prescribing at least a partial correction, depending on other signs and symptoms and the effect of a diagnostic prescription on those signs and symptoms.
Myopia in children, infants
“Prescribing for hyperopia and astigmatism is far more art than science,” according to Dr. Fern, but treatment of myopia in infants and small children is a bit more universally approached.
Small amounts of myopia are tolerated in children until they begin to engage in preschool activities, which often require good distance vision for group viewing activities, according to Dr. Schmidt.
Because a baby’s interest is in objects within reach, moderate amounts of myopia do not interfere with visual development as long as it does not exceed about 1 to 2 D. Optometrists routinely undercorrect higher myopes about 1 D until the preschool age as well.
Spectacles or contact lenses
Contact lenses are not routinely fitted on infants without significant unilateral impairment, such as aphakia. Dr. Fern has treated a number of aphakic infants with silicone elastomer lenses. If a child of 2½ years of age is significantly anisometropic, she will often fit a soft contact lens on the eye with the higher prescription to lessen image size differences and the prismatic effect of spectacles.
She prefers to use a soft spherical lens and correct astigmatism in spectacles over the top if necessary to achieve the best visual response. She has corrected one child who was 1 year old with a rigid gas-permeable contact lens for severe irregular astigmatism resulting from trauma, but for the most part, she waits until the child is about 2½ years old to fit contact lenses.
For non-anisometropes, she prefers to wait until the child is about 4 years old. “I’m more comfortable fitting children with contacts if the parent is a contact lens wearer and is comfortable handling the child’s lenses,” Dr. Fern said.
For Your Information:
- Bruce Moore, OD, is Marcus Professor of Pediatric Studies at New England College of Optometry. He may be reached at 424 Beacon St., Boston, MA 02115; (617) 236-6309; fax: (617) 236-6340; e-mail: mooreb@ne-optometry.edu.
- Paulette P. Schmidt, OD, MS, FAAO, is associate professor of optometry and physiological optics at the Ohio State University College of Optometry. She may be reached at A-324 Starling Loving Hall, 338 W. 10th Ave., Columbus, OH 43220; (614) 292-3189; fax: (614) 688-5603 or (614) 292-1683; e-mail: schmidt.13@OSU.edu.
- Karen Fern, OD, FAAO, is associate professor and director of Pediatric Optometry Residency at the University of Houston College of Optometry. She may be reached at 4901 Calhoun, Houston, TX 77204; (713) 743-1941; fax: (713) 743-2053; e-mail: kfern@uh.edu.