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Achromatopsia or Achromatopia

Achromatopsia or Achromatopia. Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS jtfulton@sightresearch.net. Achromatopsia or Achromatopia. Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS jtfulton@sightresearch.net. Achromatopsia (with or without an S).

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Achromatopsia or Achromatopia

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  1. Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS jtfulton@sightresearch.net Nat. Fed. Blind--Dallas, Texas

  2. Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS jtfulton@sightresearch.net

  3. Achromatopsia (with or without an S) • Terminology • History of color vision abnormalities • How visual system operates • Simple tests • Analysis of survey • Conclusions

  4. 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

  5. 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

  6. 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

  7. History of Abnormalities • Dyschromatopia, an ancient disease • Protanopia– Lack of Red sensitivity • Deuteranopia– No Red/Green discrimination • Tetartanopia– No Blue/Green discrimination

  8. 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

  9. How Vision Operates • Failure inResult • 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

  10. How Vision Operates • Saturation Result 5B, 5C and 5D AchromatopSia-- nystagmus 6B and/or 6C Dyschromatopia-- no nystagmus

  11. Human Visual Spectrum

  12. Saturation in Vision Channels

  13. 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

  14. 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

  15. 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

  16. 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  Analysis of Survey

  17. 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 (@ 10nm resol.) • Review this presentation if appropriate • Do not expect quick results from genetics • # of failure modes exceed the # of mutations

  18. Stimulus-response graphs

  19. 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.

  20. Where are the Rods • Baylor team, 1987 • Found “red-rods” & “green-rods,” no “rods!” • Stockman & Sharpe have • taken 100’s 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

  21. Where are the rods? • Roorda & Williams (1999), 1o nasal eccen.

  22. Recent attempts to identify Rods/Cones • Osterberg (1962)

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