Dopamine transporter (DAT) single-photon emission tomography (SPECT) with 123I-N-omega-fluoropropyl-2-beta-carbomethoxy-3-beta (4-iodophenyl) nortropane (123I-FP-CIT) is a widely used diagnostic tool for patients with suspected parkinsonian syndromes such as Parkinson’s disease, PSP, and CBD as an in vivo marker of nigrostriatal neuron loss (Palermo and Ceravolo, 2019). This evidence concerns the gene SLC6A3 and red-green color blindness.