[Lewis Thomson (OP)]

Trynt asks:

I have dichromatic eyes but with a case that has both Heterochromia iridis (different coloured eyes) and Heterochromia iridum (different colours in one eye). I have one full blue eye and the other is green with a spot of brown that can change from a spec of brown to over half brown with no pattern to the brown size at all. I have done my research on both but I'm curious as to how rare it is to have both at the same time?

What do you think?

[chris]

You are very rare!

It is hard to provide you with a crystal clear answer to your question because the genetic basis of eye colour is not completely understood. Also, there are a range of reasons why an individual may have both differently-pigmented irises and differential pigmentation within an iris. These include genetic inheritance, drugs, trauma and acquired conditions that crop up during life.

We know that eye colour is a "polygenic" trait, meaning that the combined contributions of multiple genes produce the resulting clinical feature; we also know that there are at least two colour-coding genes, EYCL3, which is located on chromosome 15 and encodes brown or blue eye colours, and EYCL1 on chromosome 19, which codes for green and blue. Varying the relative levels of expression of these genes within the iris of each eye will produce differences in pigmentation and hence colour. Exactly how this is happening in you though is hard to say!