WORDS: Dr. Paige Laudicina, Eye Center, Inc
Much like the fact that we are not born with the innate ability to recite our ABCs and 123s, we are not born with innately perfect vision, either. It’s a process for the visual system to develop, one that typically occurs through a series of events and along an average time-line. In this article I thought I’d discuss that average timeline, and when monitoring imperfections, versus intervening with glasses or other treatments, is most beneficial for a child.
In our infancy (birth to 18 months) there is a great deal of self-regulating of the visual system occurring, with the ultimate goal of low hyperopia (far-sightedness) by approximately 12 to 18 months. (1) This process of clear vision gradually developing over time is referred to as emmetropization.
This means that depending on image clarity at birth, and the effort it takes to form a clear image, our eyes grow in length in order to help create the clearest image, using the least amount of effort. The length of the eye is the factor that most dictates our refractive error throughout childhood. (Other factors include the curvature of the cornea and the thickness of the ocular lens).
By the time a child reaches their toddler years (two-five years old), if the emmetropization process was successful, one should have a low amount of hyperopia. If emmetropization has not occurred properly, this is the time where it could be appropriate to intervene by prescribing glasses. Specifically, glasses are considered at this point when hyperopia is more than +3.50D, there is a moderate amount of astigmatism, and/or there is a large difference in refractive error between the two eyes. (2)
Prescribing glasses in these cases may be necessary to prevent visual discomfort and/or amblyopia. More simply, I personally try to avoid prescribing glasses at this age, unless I have reason to believe that not prescribing may be detrimental to a child’s vision, long term.
When emmetropization has not occurred by childhood, (ages five-13), we typically begin to see an increased incidence of myopia (near-sightedness) and myopic progression. Myopia is the most frequent cause of correctable vision impairment worldwide, and by the year 2050, many studies indicate there will be nearly one billion myopes.
The inheritance pattern of myopia is multifactorial and complicated, but a child’s risk of becoming myopic is increased if he or she has myopic parents and/or siblings. Also, as a general rule, the younger a child is when found to be myopic, the more myopic they will likely become. Children who are diagnosed before the age of 7 seem to have the highest risk of progression. (3)
I find the parents of my near-sighted patients are commonly disheartened when their child’s prescription gets worse from one year to the next. I understand the concern, and according to the child and the situation, we may discuss how this is a normal part of development and nothing to fear, or we may discuss potential methods of reducing myopia progression.
Something to consider in terms of myopic progression, is that as a child ages, the risk of myopic growth becomes more influenced by their environment and daily activities. For example, more time spent outdoors can reduce the risk of myopia progression, and the risk of progression is lowest when two hours per day is spent outdoors. Alternatively, the risk of myopia progression is highest when there is three or more hours per day spent conducting close vision tasks. (3,4) This is something especially important to consider, given the increased use of digital devices these days.
In summary, the development of a child’s visual system is a complex and dynamic process that should be monitored by an eye care professional. There are trends we expect to observe over time, and situations that may require intervention to benefit the child and their vision. By obtaining an annual dilated eye exam, you can rest assured you are doing all you can to maximize your child’s potential for clear vision.