What is an optical isomer?

Optical isomers are a form of stereoisomers which are chemical species with the same structural formula, but have a different arrangement of atoms in 3-dimensional space. Optical isomers are characterised by being non-superimposable mirror images of one another and are commonly seen in organic structures with chiral carbons. They were named optical isomers since scientists first distinguished between them by the way they rotate the plane of polarised light in different directions.