You can obtain Arctic Miru Eyes from Arctic Mirus of course, by either killing them or harvesting from them after taming them to become your Pets and feeding them their favorite Food.
Arctic Mirus are aggressive Creatures (except on game worlds with the "Pro" world option "peaceful creatures" enabled) that will spawn on Peakstone in Mountains and nowadays also on Snow on frozen Oceans, in Taigas, snowy Tundras and Frozen Deserts.
Arctic Mirus can only spawn in darkness, and they cannot stand sunlight - just like all Night Creatures, they will burn away in blue flames when sunlight hits them.
Arctic Miru Eyes are needed as crafting-ingredients for Diamond Swords and Fire Resistance Potions.
You cannot use these eyes in recipes as an alternative for ordinary fiery orange Miru Eyes nor vice versa.