I have heard that those with triple iris eyes were said to be psychic, clairvoyant, etc. Is this true if so in what myths does this concept appear.
I believe you mean the concept of the Third Eye, which originated in Hindu mythology.
The third eye (also called the mind's eye, or inner eye) is a mystical and esoteric concept of a speculative invisible eye, usually depicted as located on the forehead, which provides perception beyond ordinary sight.
Paraphrasing the Rig Veda:
After the death of his lover Sati, Shiva withdrew from all society and in pain, he started to meditate. His meditation was so deep that the other gods could not wake him, even after Sati was reborn as Parvati.
Finally, the gods sent Kama, the god of love, to wake Shiva. Kama thought that using one of his arrows would do the trick but after the arrow struck Shiva, the third eye opened up and sent a flame engulfing Kama.
When Shiva’s meditation was broken, he did experience desire for Parvati but instead of letting his desire win, Shiva’s anger became greater and a third eye opened up in his forehead.
I think the idea that polycoria is linked to special powers must be rather widespread.
Apart from the "third eye" of Indian tradition, we find in Irish tradition the hero Cú Chulainn has multiple pupils. According to Britannica: "His prowess was increased by the gift of seven fingers on each hand, seven toes on each foot, and seven pupils in each eye." It's been a while since I read the Ulster Cycle, but I don't recall him being clairvoyant or psychic per se. He certainly exhibited great physical strength, endurance, agility and beauty beyond that of most other men.