Yes, it is possible for a square planar complex to have optical isomers, although it is relatively rare. Optical isomers, or enantiomers, are molecules that are non-superimposable mirror images of each other. For a square planar complex to exhibit optical isomerism, it must have a specific arrangement of ligands that leads to chiral configurations.
In a typical square planar complex, if all four ligands are different, then the arrangement can create two non-superimposable mirror images, resulting in optical isomers. An example of this would be a complex like [Pt(NH3)2(Cl)2], where the two ammonia molecules and two chloride ions can arrange themselves in a way that produces chiral forms.
However, if the ligands are similar or if there is a plane of symmetry present in the structure, the complex will not display optical isomerism. Therefore, the possibility of optical isomers in square planar complexes relies heavily on the ligand environment and symmetry of the complex.