Is myopia heritability 90%?

[t689]

I read 1 in 5, but I don't believe it.  I think it's more like realistically speaking low 80 percentage and up, reaching 99% for two parents.  If I'm wrong, please correct me.

[JohnHaganMD]

The hereditary genetics of myopia are incompletely understood and, unlike other genetic diseases, it is not possible to give exact figures for developing glaucoma from any father and mother. In my family I'm the only myopic person.

[t689]

so you have children?

[JohnHaganMD]

One myopic like me; one hyperopic like my wife

[t689]

It seems to me that myopia genetics is maybe most like height, where your offspring takes basically one copy from your two sets of genes and one copy from the other parent.  So if one of my parents had perfect vision, I probably have exactly half good genes and bad genes for vision and my myopia is moderate.  So let's I have AaBbCc combined with other parent of AABBCC where A,B,C are good vision, a,b,c poor vision.  I have moderate vision because I have AaBbCc, half good, half bad.  If I mate with AABBCC, then offspring choices are: 2 of AABBCC, 2 of AaBbCc, so the offspring in this simple example would have a 50% of having perfect vision and a 50% chance of having moderate myopia like me depending on the chance probabilities of which genes are selected from me and somebody with perfect vision.  This seems to make sense because then the odds of having  the first two children myopic are 1 in 4, or all three 1 in 8.  So even though it might be 50% the more children you have the less likely all of them would be myopic.

[t689]

I will also say one other thing.  My mother had moderate myopia combined with a person with perfect vision.  I can see how in a family of two you can have two in a row with myopia.  Let's say the first child got the eight ball.  Then the odds for the second child are still 50-50, I just as likely were to not have myopia as myopia but I got the mix.  But over the law of large numbers, it could just as likely as been that my sister and I did not get myopia.  My sister married somebody with myopia as well, and the first child has vision stabilised at 20/40, the second at 20/110 and her vision was rather similar to mine.  So it's clear that two parents are contributing to twice the odds of having myopia.  If she married somebody without glasses, it could very well have been 20/20.  And since the vision was so low, there must be some protective mechanism of myopia genes before they balloon out of control as in the asian populations.

[JohnHaganMD]

Would it were that simple Mendel would have used myopia for his studies instead of green peas

[t689]

Well I'll answer my own question.  I did read one study where they identified certain genes among those who ended up getting myopia which was shared in some cased with those not myopic.  Those who had those genes were 40% likely to survive without glasses.  So if you have three children, I would say the odds speaking you'd have two children without glasses half the time and one children out of the three the other half, just on sheer odds that would make sense.