title: Visual functions in phenylketonuria-evaluating the dopamine and long-chain polyunsaturated fatty acids depletion hypotheses.
abstract: BACKGROUND
  In phenylketonuria presymptomatic treatment following newborn screening prevents severe mental and physical impairment. The reasons for subtle impairments of cerebral functions despite early treatment remain unclear. We assessed a broad spectrum of visual functions in early-treated patients with phenylketonuria and evaluated two hypotheses-the dopamine and the long-chain polyunsaturated fatty acids (LCPUFAs) depletion hypotheses.
  
  
  METHODS
  Contrast sensitivity, colour vision, electroretinography, frequency doubling technology campimetry (FDT), and their relation with blood phenylalanine and docosahexaenoic acid levels were assessed in 36 patients with phenylketonuria and 18 age-matched healthy controls.
  
  
  RESULTS
  Contrast sensitivity was significantly lower and total error scores in colour vision significantly higher in patients than controls. Electroretinography results differed significantly between patients and controls. We found a trend for the effect of phenylalanine-levels on contrast sensitivity and a significant effect on colour vision/FDT results. Docosahexaenoic acid levels in erythrocytes were not associated with visual functions.
  
  
  CONCLUSIONS
  This is the first evaluation of visual functions in phenylketonuria using a comprehensive ophthalmological test battery. We found no evidence supporting the long-chain polyunsaturated fatty acids depletion hypothesis. However, the effect of phenylalanine-levels on visual functions suggests that imbalance between phenylalanine and tyrosine may affect retinal dopamine levels in phenylketonuria. This is supported by the similar patterns of visual functions in patients with phenylketonuria observed in our study and patients with Parkinson's disease.
authors.affiliation: Centre for Paediatric and Adolescent Medicine, University of Heidelberg, Department of General Paediatrics, Division of Metabolic Disorders, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany. gwendolyn.gramer@med.uni-heidelberg.de
authors.forename: Gwendolyn
authors.initials: G
authors.lastname: Gramer
authors.forename: Birgit
authors.initials: B
authors.lastname: Förl
authors.forename: Christina
authors.initials: C
authors.lastname: Springer
authors.forename: Petra
authors.initials: P
authors.lastname: Weimer
authors.forename: Gisela
authors.initials: G
authors.lastname: Haege
authors.forename: Friederike
authors.initials: F
authors.lastname: Mackensen
authors.forename: Edith
authors.initials: E
authors.lastname: Müller
authors.forename: Hans Eberhard
authors.initials: HE
authors.lastname: Völcker
authors.forename: Georg Friedrich
authors.initials: GF
authors.lastname: Hoffmann
authors.forename: Martin
authors.initials: M
authors.lastname: Lindner
authors.forename: Hermann
authors.initials: H
authors.lastname: Krastel
authors.forename: Peter
authors.initials: P
authors.lastname: Burgard
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D055253:Color Vision; D015350:Contrast Sensitivity; D004298:Dopamine / Q000378:metabolism*; D004596:Electroretinography; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D010661:Phenylketonurias / Q000378:metabolism / Q000503:physiopathology*; D014785:Vision, Ocular; D055815:Young Adult
chemical_list: D005231:Fatty Acids, Unsaturated; D004298:Dopamine