Achromatopsia or Achromatopia

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Achromatopsia or Achromatopia

• Achromatopia or Dyschromatopia
• James T. Fulton
• VISION CONCEPTS
• jtfulton_at_sightresearch.net

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Achromatopsia or Achromatopia

• Achromatopia or Dyschromatopia
• James T. Fulton
• VISION CONCEPTS
• jtfulton_at_sightresearch.net

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Achromatopsia (with or without an S)

• Terminology
• History of color vision abnormalities
• How visual system operates
• Simple tests
• Analysis of survey
• Conclusions

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AchromatopSia(with or without an S)

• Past clinical practice was indiscriminate
• Term seldom used in academic circles
• Oliver Sacks popularized term with an S
• Futterman used term with an S
• Used here to indicate Syndrome

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Achromatopia(without an S!)

• A simple concept in academia
• Achromat--(n. Latin without color)
• Achromatope A person lacking color vision
• Achromatopia A one symptom disease
• Dyschromatopia-- (Latin with abnormal color)
• Unilateral Achromatopia No color in one eye
• Monochromat Has only one type of receptor

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AchromatopSia(with an S!)

• A Syndrome rather than a single symptom
• Hemeralopia Abnormal sensitivity to light
• Nystagmus Uncontrolled wandering eye(s)
• Dyschromatopia Abnormal color vision
• Amblyopia Low visual acuity (with correction)
• Strabismus Abnormal convergence of eyes

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History of Abnormalities

• Dyschromatopia, an ancient disease
• Protanopia Lack of Red sensitivity
• Deuteranopia No Red/Green discrimination
• Tetartanopia No Blue/Green discrimination

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History of Color Vision

• Day vs Night vision-- ancient observation
• 1 Photopic vision-- A wide color spectrum
• 2 Scotopic vision Lacking in color
• Long described as a rod/cone dichotomy
• Actually due to operation of red channel
• Rods not required, or found in modern theory

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How Vision Operates

• Failure in Result
• 2 or 5B Tritanopia (rare)
• 3 or 5C Pentanopia (rarer)
• 4 or 5D Protanopia
• 6B Blue/Green achrom. (tetartanopia)
• 6C Red/Green achrom. (deuteranopia
• 7 Right hemiachromatopia
• 8 Left hemiachromatopia
• 9 Achromatopia
• 10 Nystagmus, Strabismus a/o
  Amblyopia

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How Vision Operates

• Saturation Result
• 5B, 5C and 5D AchromatopSia-- nystagmus
• 6B and/or 6C Dyschromatopia-- no nystagmus

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Human Visual Spectrum
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Saturation in Vision Channels
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Analysis of Survey

• Terminology is a problem
• Rod monochromacy is obsolete
• AchromatopSia separate from Achromatopia
• Atypical or incomplete ? dyschromatopia
• Most office diagnoses are incomplete
• Spectral exam critical to diagnoses

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Analysis of Survey

• Most office diagnoses are incomplete
• Reliance on Ishahara Plates History
• Reliance on acuity measurements
• No spectral measurements
• ERG (if performed) at only two levels
• A mid-level ERG can substitute for a spectra
• A level of 10 of the maximum is suggested
• Only one respondent with genetic testing

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On Genetic Testing

• Only one respondent tested genetically
• Exhibits all symptoms of achromatopSia
• CNGB3 mutation in both copies
• BUT, spectrum appears to be normal
• failure modes EXCEEDS gene mutat.
• Need greater specificity among patients

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Analysis of Survey

• 25 Participants
• Diagnosis
• 2 Total Achromats
• 2 Total Achromatopsia
• 12 Achromatopsia
• 3 Incompl. Achro-opsia
• 3 Cone dystrophy
• 1 Rod Monochromat
• 1 no diagnosis

• Alternate
• 2 AchromatopSia
• 10 Achromatopia
• 12 Dyschromatopia
• ?? Hemeralopia
• 0 Cone dystrophy
• 0 Rod Monchromats
• 1 Tetrachromat ??

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Recommendations

• Achromatopsia.org provide guidelines
• For categorizing people with abnormal color
• Individuals suggest their doctors
• Perform a 3-level ERG or
• Perform a spectral evaluation (_at_ 10nm resol.)
• Review this presentation if appropriate
• Do not expect quick results from genetics
• of failure modes exceed the of mutations

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Stimulus-response graphs
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Rods/Cones vs Photoreceptors

• Two Classes Rods and Cones
• Have been defined based on light sensitivity
• Have been defined based on spectral selectiv.
• Have been defined on Outer Segment shape
• Have been defined on Inner Segment shape
• Have been defined versus location in retina
• None of these have stood the test of time
• The spectra of a rod matches the blue and green
  spectra combined.

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Where are the Rods

• Baylor team, 1987
• Found red-rods green-rods, no rods!
• Stockman Sharpe have
• taken 100s of hi-resolution pix of the retina
• Only one report claimed to locate rods
• Folklore says rod density highest at 10o
• Data of Freiding et al. (2007)
• Show same spectrum on-axis at 10o

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Where are the rods?

• Roorda Williams (1999), 1o nasal eccen.

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Recent attempts to identify Rods/Cones

• Osterberg (1962)