title: Vision in observers with enhanced S-cone syndrome: an excess of s-cones but connected mainly to conventional s-cone pathways.
abstract: OBJECTIVE
  The effect of increased numbers of S-cone photoreceptors in enhanced S-cone syndrome (ESCS) was investigated psychophysically in six ESCS observers to understand more about relative cone sensitivities and postreceptoral organization.
  
  
  METHODS
  Measures of temporal sensitivity or delay were made: S- and L-cone temporal acuity (critical flicker fusion, or CFF), S-cone temporal contrast sensitivity, and S-cone delay.
  
  
  RESULTS
  ESCS observers showed uniform enhancements of S-cone CFF of between 0.85 and 6.25 Hz, but reductions in L-cone CFF. They also showed higher S-cone temporal contrast sensitivities at medium and high S-cone adaptation levels, with sensitivity functions that peaked near 7.5 Hz but fell off at lower and higher frequencies. In contrast, the mean normal function was flat at low frequencies and fell off only at high frequencies. The S-cone signal, as in the normal, is subject to large phase delays.
  
  
  CONCLUSIONS
  We interpret the enhancements in CFF as increases in S-cone number in ESCS of between 1.39 and 11.32 times normal density (with a mean of 3.48). The peaked ESCS contrast-sensitivity functions are consistent with S-cone signal interactions that increase sensitivity at intermediate frequencies through constructive interference but decrease it at lower and higher frequencies through destructive interference. Measurements of S-cone delays relative to L- and M-cone signals show that the predominant S-cone signals in ESCS are negative and delayed as in normal observers, but reveal another faster, positive S-cone signal. This signal is also likely to be the cause of constructive and destructive interference in the contrast-sensitivity data of ESCS observers.
authors.affiliation: UCL Institute of Ophthalmology, University College London, London, United Kingdom.
authors.forename: Caterina
authors.initials: C
authors.lastname: Ripamonti
authors.forename: Jonathan
authors.initials: J
authors.lastname: Aboshiha
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Henning
authors.forename: Panagiotis I
authors.initials: PI
authors.lastname: Sergouniotis
authors.forename: Michel
authors.initials: M
authors.lastname: Michaelides
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Moore
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Webster
authors.forename: Andrew
authors.initials: A
authors.lastname: Stockman
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D004596:Electroretinography; D015785:Eye Diseases, Hereditary / Q000503:physiopathology*; D005425:Flicker Fusion / Q000502:physiology; D006801:Humans; D057093:Orphan Nuclear Receptors; D010775:Photic Stimulation; D011601:Psychophysics; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012162:Retinal Degeneration / Q000503:physiopathology*; D014786:Vision Disorders / Q000503:physiopathology*; D014785:Vision, Ocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology
chemical_list: C403073:NR2E3 protein, human; D057093:Orphan Nuclear Receptors
keywords: NR2E3; critical flicker fusion; enhanced S-cone syndrome; flicker sensitivity; short-wavelength-sensitive cones; temporal acuity; temporal processing