Why Perfect Eyesight Might Not Be So Perfect.
Perfect eyes with zero prescription. Couldn’t be better, yeah?
While this may be so for adults, the same doesn’t necessarily hold true with children’s eyes.
You see (no pun intended), children are usually born long-sighted, or far-sighted. From birth, children’s eyes grow longer in length over time. This developmental change is a coordinated process called emmetropisation, where the length of the eye and the power of its focusing components balance out and, if the process occurs correctly, the child develops and maintains normal vision while growing up.
But there are tell-tale signs that a child may not develop normal vision. One of these signs is when a child has a lower-than-expected amount of hyperopia (the medical term for long-sightedness) for their age.
A child at age 5 should have around +1.50 degree of hyperopia, which is expected to decrease over time with the emmetropisation process. I explain to parents that, no, being mildly long-sighted doesn’t mean their child needs to wear glasses. Unlike adults, young children have very flexible focusing systems that allow them, in most cases, to effortlessly compensate for this level of long-sightedness and see clearly both near and far without the need for glasses. (Some children who have focusing weaknesses may need reading glasses, but that’s for another topic).
What is a red flag to me in my children’s eye care clinic is when a young child presents with a low amount of long-sightedness (+0.75 or less), or perhaps even zero amount of long-sightedness. A prescription of zero at age 5 or 6 is not normal, and is one of the key indicators that the child may imminently become myopic (short-sighted, or near-sighted).
Children with less-than-normal amounts of long-sightedness for their age are at high risk of developing short-sightedness—that is, blurred vision in the far distance. It means their eyes have already grown longer than expected at their age and have little or no buffer against becoming short-sighted. And once a child is myopic, their eyes usually get worse and worse.
So while parents may think their 5 year old child with zero prescription is blessed to have such ‘perfect’ eyesight, the reality is that this child may not maintain good vision for long and needs to be watched very closely, perhaps as regularly as every 6 months. At the earliest signs of short-sightedness, treatment—such as low-dose atropine eye drops—can be initiated to help slow the rapid vision deterioration that often occurs with childhood myopia.
This is one of the reasons why all children should have a baseline comprehensive eye examination at an optometrist by the age of 3 and certainly before they start school, even if they show no signs of having vision problems. Basic vision screening tests, while helpful at identifying gross vision problems, are not a subsitute for an in-depth optometric assessment that can reveal more subtle issues.
By establishing an accurate baseline of a child’s level of vision and focusing status from a young age we can assess their risk of developing vision issues and can even predict when the child may become short-sighted. The earlier we can catch a child’s vision changes and implement an appropriate myopia management strategy, the more likely he or she can maintain good vision with less dependency on glasses to see.
If your child hasn’t yet had their first eye test, I encourage you to arrange a consultation with an optometrist suitably experienced and equipped to test young children’s eyes.