May 2003
Volume 44, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2003
The Relationship Between ERG Measures of Phototransduction Efficiency and Genotype in Retinitis Pigmentosa
Author Affiliations & Notes
  • P. Kozma-Wiebe
    Retina Foundation Southwest, Dallas, TX, United States
  • K.G. Locke
    Retina Foundation Southwest, Dallas, TX, United States
  • D.H. Wheaton
    Retina Foundation Southwest, Dallas, TX, United States
  • D.C. Hood
    Department of Psychology, Columbia University, New York, NY, United States
  • D.G. Birch
    Department of Psychology, Columbia University, New York, NY, United States
  • Footnotes
    Commercial Relationships  P. Kozma-Wiebe, None; K.G. Locke, None; D.H. Wheaton, None; D.C. Hood, None; D.G. Birch, None.
  • Footnotes
    Support  EY05235FFB
Investigative Ophthalmology & Visual Science May 2003, Vol.44, 1863. doi:
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      P. Kozma-Wiebe, K.G. Locke, D.H. Wheaton, D.C. Hood, D.G. Birch; The Relationship Between ERG Measures of Phototransduction Efficiency and Genotype in Retinitis Pigmentosa . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1863.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: Photoreceptor activity in humans can be studied by analyzing the a-wave of the electroretinogram (ERG) recorded to high intensity lights. Our aim was to determine the degree to which abnormalities in phototransduction parameters are associated with specific disease-causing mutations. Methods: Dark- and light-adapted ERG a-wave responses to white flashes were recorded in patients with widespread retinal degeneration associated with RPGR (n=7), CRX (n=6), RP1 (n=4), RDS/Peripherin (n=34), Rhodopsin (RHO) (n=28) and ABCR (n=12) mutations. Rod and cone transduction efficiency (S) in each patient was compared to normal values based on 100 normal subjects (Birch et al, 2002). S was measured by the method described by Hood and Birch (1997). Four high flash intensities, ranging from approximately 3.2 to 4.4 log scot td-s, were presented first to the dark adapted eye and then on a rod-saturating background (3.2 log td). Rod-only responses were derived by the subtraction of light-adapted responses from the dark-adapted ones. Results: Rod S values were lower than the lower limit of normal for most patients with RHO (mean ΔS:-0.36) and ABCR (mean ΔS:-0.41) mutations but were within normal limits for other mutations. In the RHO group, patients with Pro23His mutation had low rod S values (mean ΔS:-0.49) whereas patients with other RHO mutations had values within, or close to, the normal range. Rod S values did not vary systematically with age. Cone S values were below the lower limit of normal in all mutations with the exception of RDS/Peripherin. In general, cone S values were more variable and lower after age 40. Conclusions: The decreased rod photosensitivity in many patients with RHO mutations is consistent with an abnormality that affects the activation of phototransduction. The normal or close to normal rod S values in other mutations indicates that they do not play a role in the activation process. The diminished cone S values in all patients except those with RDS/Peripherin mutations are presumably secondary effects since the mutations studied here primarily affect rods. These results suggest that ERG measures may be helpful for identifying patients likely to have mutations influencing the sensitivity of phototransduction.

Keywords: electroretinography: clinical • photoreceptors • mutations 
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