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Visual functions in phenylketonuria-evaluating the dopamine and long-chain polyunsaturated fatty acids depletion

Gwendolyn Gramer1, Birgit Förl, Christina Springer

  • 1Centre 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

Molecular Genetics and Metabolism
|December 11, 2012
PubMed

Insights

Early treatment for phenylketonuria (PKU) improves outcomes, but subtle visual impairments persist. This study found phenylalanine levels, not LCPUFAs, impact visual functions, suggesting dopamine imbalance may be involved.

Area of Science:

  • Neuroscience
  • Ophthalmology
  • Metabolic Disorders

Background:

  • Newborn screening enables presymptomatic treatment for phenylketonuria (PKU), preventing severe impairment.
  • Subtle cerebral function deficits persist in early-treated PKU patients, with underlying causes unclear.
  • Investigated the dopamine and long-chain polyunsaturated fatty acids (LCPUFAs) depletion hypotheses for visual dysfunction in PKU.

Purpose of the Study:

  • To comprehensively assess a wide range of visual functions in early-treated PKU patients.
  • To evaluate the roles of phenylalanine and LCPUFAs in visual impairments associated with PKU.
  • To explore potential mechanisms linking PKU to visual system dysfunction.

Main Methods:

  • Assessed contrast sensitivity, color vision, electroretinography, and frequency doubling technology campimetry (FDT).
  • Correlated visual function parameters with blood phenylalanine and docosahexaenoic acid (DHA) levels.
  • Compared 36 early-treated PKU patients with 18 age-matched healthy controls.

Main Results:

  • PKU patients exhibited significantly reduced contrast sensitivity and impaired color vision compared to controls.
  • Electroretinography results were significantly different between PKU patients and controls.
  • Phenylalanine levels showed a trend affecting contrast sensitivity and significantly impacted color vision/FDT; DHA levels were not associated with visual function.

Conclusions:

  • This study provides the first comprehensive ophthalmological evaluation of visual functions in PKU.
  • Results do not support the LCPUFA depletion hypothesis in PKU-related visual dysfunction.
  • Elevated phenylalanine levels may disrupt retinal dopamine balance, impacting visual function, similar to patterns seen in Parkinson's disease.
Abstract

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