Dopamine; Macular retinal vessel density; Macular thickness; Optical Coherence Tomography Angiography, (OCTA); Optical Coherence Tomography, (OCT); Optical coherence tomography angiography; Parkinson's disease, (PD); Phenylalanine level; Phenylalanine, (Phe); Phenylketonuria; Tyrosine, (Tyr); aminoacid supplements, (AAS); axial length, (AL); contrast sensitivity, (CS); deep capillary plexus, (DCP); diopters, (D); dopamine, (DA); early treated phenylketonuria, (ETPKU); external limiting membrane/inner segment of photoreceptors/outer segment of photoreceptors, (ELM/IS/OS); ganglion cell complex, (GCC); ganglion cell layer, (GCL); inner limiting membrane, (ILM); inner nuclear layer, (INL); inner plexiform layer, (IPL); inner retinal layer, (IRL); intraocular pressure, (IOP); outer nuclear layer, (ONL); outer plexiform layer, (OPL); outer retinal layer, (ORL); phenylalanine hydroxylase gene, (PAH); phenylketonuria, (PKU); retinal nerve fiber layer, (RNFL); retinal pigment epithelium, (RPE); signal strength index, (SSI); sine-wave contrast test, (SWCT); spectral domain, (SD); spherical equivalent, (SE); split-spectrum amplitude-decorrelation angiography, (SSADA); superficial capillary plexus, (SCP); tetrahydrobiopterin, (BH4); total retinal layer thickness, (TRLT); vessel density, (VD); visual acuity, (VA); visual evoked potential, (VEP)