I don't think it can be an optical illusion, but there may be something I don't know about that. Generally, if an imaging system was going to cause a distortion, perspective lines would either a) converge, b) diverge, c) form a "pincushion" (think black hole), or d) create barrel distortion (opposite of black hole). I've never seen an optical system create two sets of parallel lines from one set, like this highlighted image.