Article: Why More Firstborn Kids Need Glasses

[Steve Machol]

After controlling for age and sex, the researchers saw that first children were about 12% more likely to be nearsighted than second children. This was similar to the finding of the earlier study with younger subjects. Firstborns were also 21% likelier than second-borns to have severe myopia. And when compared to people born fourth or later, firstborns were almost 40% more likely to be nearsighted. (The researchers counted only children as firstborns too, but the results were the same when they removed only children from the analysis.)

What do you think?

http://blogs.discovermagazine.com/in.../#.WLS0QRIrJR5

FWIW, I'm the oldest of four children and I'm the only myope.

[Pete Hanlin]

Well, I'm the oldest of three boys and (prior to LASIK 16 years ago) I am a -4.75 sph myope. Other than a bit of astigmatism for the youngest sibling, both my brothers are emmetropes... I'm also the only one of the three of us to complete college, so the article's assumption on that factor is also true in my particular case.

The causal factors of myopia make for a fascinating study (at least for me). Here's a link to a paper on the relationship between exposure to sunlight and the development of myopia I recently read- interesting stuff: http://www.pointsdevue.com/sites/def...utm_medium=PDF

[Steve Machol]

Well, I'm the oldest of three boys and (prior to LASIK 16 years ago) I am a -4.75 sph myope. Other than a bit of astigmatism for the youngest sibling, both my brothers are emmetropes... I'm also the only one of the three of us to complete college, so the article's assumption on that factor is also true in my particular case.

I forgot to mention that I'm also the only sibling with a college degree.

[Lelarep]

I had heard of the "First Born Theory" before. but I had no idea it had good data behind it. I'll be interested to find out if they can unravel the last part of it that is currently unknown, once differences in education are subtracted.

Also first born, also a myope, brother is also a myope, equally educated, but my myopia presented very early in childhood, his didn't hit until after college. Mine is also much worse than his. He's only ~ -1.50, I'm -4.50. We're twins, so that makes it ever more interesting. I've be interested to see a twin study, does the "first born" hypothesis hold up with twins?

[Pete Hanlin]

Interesting question about twins... Assuming most of the differences are due to the difference in experiences between first and later borns (nurture), vs. actual biological differences between first and later borns (nature), I would guess the differences with twins are going to be negligible.
[Side note- I really like that term "later borns," I'll have to start using that when addressing my brothers- after all, I spent most of our childhood convincing them that they were adopted.]

Personally, I think for most individuals the progression of myopia is primarily influenced by environment/activities. If I recall correctly, there were actually studies in Japan that indicated during WWII (when schoolwork was suspended) incidence of myopia dropped. Then, after WWII (school resumed) myopia levels rose back to previous levels (I think that study was referenced in Borish's Clinical Refraction, it's been decades since I read it but it obviously stuck with me).

The idea that exposure to blue light decreases progression of myopia (which is suggested by the study at the link I posted earlier) makes sense, optically speaking. In the old days, if you were a book worm who spent all day inside reading, you only saw incandescent light- which is skewed toward red. Even in an emmetropic eye, red light is focused slightly behind the retina- and it is not hard to imagine there is a biological mechanism that would cause the eye to elongate to create better focus. Blue light has a shorter focal length, so there's no/less of a signal to elongate. Just a thought...

[AngeHamm]

My family of eight kids is exactly the opposite. The oldest four never needed correction for distance, the younger four all do.

[Browman]

Interesting. I'm my parents' only biological child and a myope; my adopted brother, who was the elder of two siblings, has 20/10 vision, although his biological father is a lifelong myope.

[smallworld]

I wonder if the "play outside" to avoid myopia progression applies, as the oldest child doesn't have a playmate.

[gaspoweredrobot]

Just throwing another anecdote out there:

Youngest of four brothers, I played outside until the Super Nintendo came out when I was nine. Between that and the Internet showing up in people's homes, my vision dropped dramatically (I'm now -3.75 OU with minor cyl) around age 9-11, while all three of my brothers get on just fine with no correction. They're 5, 7, and 8 years my senior, respectively, so they were too old to spend the volume of time looking at bright low-resolution screens that I was. Education-wise, I was the only one to actually finish high school, so even that's a reversal. So it's kind of funny that the outdoor play part applies quite well, but with a complete reversal of the chronology!