Iris and retina: fully genetically determined?

[nomadreid]

TL;DR Summary

The capillary arrangement in the retina that is used for the retina identification scans, and the pattern of the iris used for iris identification scan: apart from disorders, are they determined at least partly by the environment (say, in the womb, like fingerprints) or fully determined by genetics (like eye colour)?

I am posing two questions, one for each of two biometric techniques
https://en.wikipedia.org/wiki/Iris_recognition
https://en.wikipedia.org/wiki/Retinal_scan
Attempting to find the answer to the question posed in the Summary, I only get articles about hereditary eye disorders.
I am referring to the normal cases... obviously either one of these may be altered by a disorder or disease or an accident.

 

[BillTre]

Are these patterns the same in identical twins?
I suspect not.
If not, they are not completely genetically determined since identical twins have the same genetics.

 

[nomadreid]

Are these patterns the same in identical twins?

Ah. Excellent point; I hadn't thought of looking for that question.
According to https://www.ntu.edu.sg/home/AdamsKong/publication/Twin_ICBA_06.pdf
they are not. Therefore my question is answered.
Many thanks!

 

[jackwhirl]

Watch this brief and delightful video from MinuteEarth to learn more about what makes your fingerprints unique. It is reasonable to believe that similar mechanisms would affect the way your eyes grow.
Looking again at your first post, you've probably seen it.