These crystal lenses fit over the eyes. While wearing them, you have advantage on Wisdom (Perception) checks that rely on sight. In conditions of clear visibility, you can make out details of even extremely distant creatures and objects as small as 2 feet across.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.