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3 July 2008Nat. Fed. Blind--Dallas, Texas Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS

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Presentation on theme: "3 July 2008Nat. Fed. Blind--Dallas, Texas Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS"— Presentation transcript:

1 3 July 2008Nat. Fed. Blind--Dallas, Texas Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS

2 Achromatopsia or Achromatopia Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS

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

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16 How Vision Operates Failure inResult –2 or 5BTritanopia (rare) –3 or 5CPentanopia (rarer) –4 or 5DProtanopia –6B Blue/Green achrom. (tetartanopia) –6C Red/Green achrom. (deuteranopia –7 Right hemiachromatopia –8 Left hemiachromatopia –9 Achromatopia –10 Nystagmus, Strabismus a/o Amblyopia

17 How Vision Operates SaturationResult 5B, 5C and 5D AchromatopSia-- nystagmus 6B and/or 6C Dyschromatopia-- no nystagmus

18 Human Visual Spectrum

19 Saturation in Vision Channels

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21 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

22 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

23 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

24 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 

25 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

26 Stimulus-response graphs

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28 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.

29 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 10 o Data of Freiding et al. (2007) –Show same spectrum on-axis & at 10 o

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

31 Recent attempts to identify Rods/Cones Osterberg (1962)


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