Foveal cone involvement in retinitis pigmentosa progression assessed through flash-on-flash parameters

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9 Scopus citations


Purpose. To compare psychophysical Naka-Rushton parameters in retinitis pigmentosa (RP) patients and healthy controls using a flash-on-flash increment threshold paradigm, and to measure changes of these parameters with RP progression. Methods. Sixty-six RP patients and 10 normal subjects were tested, and their maximum response (R(max)), half-saturation intensity (σ), and slope (n) parameters were estimated. Results/Conclusions. R(max) in RP patients is decreased significantly with respect to the range in normal controls and continues to decrease (0.024 log units/yr) with disease progression. The distribution of σ in RP patients differs from that in normal subjects, showing lower values in general, but no progression. Small differences in parameter distributions among genetic or pathophysiologic RP subcategorizations were found, but these do not fulfill stricter statistical criteria required for multiple comparisons. Measurement noise, inherent in the flash-on-flash paradigm, exert considerable influence on the quality of the data, as was demonstrated through repeated measures and a Monte Carlo simulation.

Original languageEnglish (US)
Pages (from-to)231-242
Number of pages12
JournalInvestigative Ophthalmology and Visual Science
Issue number1
StatePublished - 1993


  • Naka-Rushton parameters
  • foveal psychophysics
  • increment threshold
  • retinitis pigmentosa

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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