Is there an actual statistic to reflect how rare it is to have identical twins with DIFFERENT eye color?

Question

We have identical twin girls. One has hazel-green eyes, the other's is blue. We are certain our girls are identical, so please do not insist that they are fraternal. Besides their eye color and a little difference in weight, they are both fairly identical. Even I sometimes confuse them in photos. Anyway, I know the occurance of diverse eye color in identicals is rare, I'm just unsure if there is an actual number associated with it.

Answer 1

The eye color is determined by about five to six genes, which makes it difficult to predict a child's eye color. In contrast to,  body height, environmental factors play almost no role in eye color; scientists say the heritability of eye color is 98% [Bito et al. (1997). Arch. Ophthalmol. 115(5):659-63].

In identical twins the genes determining eye color are of course identical, too. So, both twins SHOULD have identical eye color. BUT, in rare cases (<2%), identical twins have indeed different eye color, which has no genetic cause.  However, I have no idea which factor(s) are responsible for this.

By the way, be aware that a child's eye color often changes during the first year (usually becomes darker); sometimes the eye color even changes until adulthood (Bito et al. 1997). Identical twins may therefore have slightly different eye colors during infanthood but the same eye color as adults.

Hope this helps...in our house we have 6 children, all with brown hair and brown to hazel eyes... but one... our youngest has red hair and blue eyes... genetics is a very interesting subject!!

Hope this helped!!  

Kristy