I finally got around to reading the full article published in Ophthalmology on the Baltimore Pediatric Eye Disease study (link to the abstract, link to a press release). The study looked at nearly 2300 children ages 6 months to 5 years old. The researchers examined the children and recorded the refractive error and astigmatism to find out the prevalence of myopia, hyperopia, and anisometropia (difference in the prescription between the two eyes), in young children. They applied the prescribing guidelines of the American Academy of Ophthalmology to determine how many children would benefit from glasses at this age.
I was particularly interested in this study because it was the largest study I’ve seen that looks at very young children to see how many are wearing glasses, and how many should be wearing glasses. They also broke out the numbers by age, by race (African-American, and non-hispanic white), and type of vision problem (nearsighted, farsighted, astigmatism, or anisometropia). I’d been looking for these number for a long time, as I’d like to be able to say just how common it is for a baby or toddler to need glasses.
So here’s a run-down of some of their findings that I found particularly interesting, though not necessarily surprising:
- Severe refractive errors are uncommon at this age (like I said, the results aren’t actually surprising).
- The average refractive error for white children was +1.24, and for African-American children, it was +0.43. The astigmatism was 0.50 for white children, and 0.58 for African-American children. This number did not change significantly with age (between 6 and 72 months), and there was no gender difference.
- Of the 2,298 children examined, only 29 wore glasses – that’s 1.26%. 10 of those 29 children with glasses did not meet the prescribing guidelines (so possibly don’t need glasses at all).
- Based on the exams and prescribing guidelines, 116 of the children, or 5% of the population, would benefit from glasses.
Ok, so to break down the numbers even further, here’s how the numbers fall out for the children who did need glasses, by age and type of refractive error. It’s worth noting that the numbers are small enough that it doesn’t make sense to get caught up too much in percentages. I’ve listed the recommended threshold for glasses in parentheses.
6-11 months old (167 children examined):
myopia (-4 D or stronger): 1
hyperopia (+6 D or stronger with no esotropia, +2 D or stronger with esotropia): 2
astigmatism (3 D or stronger): 2
anisometropia (2.5 D or greater difference between eyes): 1
total: 6 of the 167 (3.6%) children needed glasses
12-23 months old (366 children examined):
myopia (-4 D or stronger): 0
hyperopia (+5 D or stronger without esotropia, +2 D or stronger with esotropia): 4
astigmatism (2.5 D or stronger): 0
anisometropia (2.5 D or greater difference between eyes): 0
total: 4 of the 366 (1%) children needed glasses
24-47 months old (887 children examined):
myopia (-3 D or stronger): 2
hyperopia (+4.5 D or stronger without esotropia, +1.5 D or stronger with esotropia): 11
astigmatism (2 D or stronger): 11
anisometropia (2 D or greater difference between eyes): 14
total: 38 of the 887 (4.2%) children examined needed glasses
48-71 months old (878 children examined)
myopia (-1.5 D or stronger) 16
hyperopia (+3.5 D or stronger without esotropia, +1.5 or stronger with esotropia): 29
astigmatism (2 D or stronger): 20
anisometropia (2 D or greater difference between eyes): 17
total: 82 of the 878 (9.3%) children examined needed glasses
It’s worth noting that the numbers may change considerably depending on location and population, but the numbers really fit with what I’ve experienced: It’s uncommon for young kids to need glasses, and sadly more children need glasses than are prescribed glasses, probably because vision exams at young ages are still not common.