Achromatopsia or achromatopia
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Achromatopsia or Achromatopia. Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS [email protected] Achromatopsia or Achromatopia. Achromatopia or Dyschromatopia James T. Fulton VISION CONCEPTS [email protected] Achromatopsia (with or without an S).

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Achromatopsia or achromatopia

Achromatopsia or Achromatopia

Achromatopia or Dyschromatopia

James T. Fulton

VISION CONCEPTS

[email protected]

Nat. Fed. Blind--Dallas, Texas


Achromatopsia or achromatopia1

Achromatopsia or Achromatopia

Achromatopia or Dyschromatopia

James T. Fulton

VISION CONCEPTS

[email protected]


Achromatopsia with or without an s
Achromatopsia (with or without an S)

  • Terminology

  • History of color vision abnormalities

  • How visual system operates

  • Simple tests

  • Analysis of survey

  • Conclusions


Achromatopsia with or without an s1
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


Achromatopia without an s
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


Achromatopsia with an s
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


History of abnormalities
History of Abnormalities

  • Dyschromatopia, an ancient disease

    • Protanopia– Lack of Red sensitivity

    • Deuteranopia– No Red/Green discrimination

    • Tetartanopia– No Blue/Green discrimination


History of color vision
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


How vision operates
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


How vision operates1
How Vision Operates

  • Saturation Result

    5B, 5C and 5D AchromatopSia-- nystagmus

    6B and/or 6C Dyschromatopia-- no nystagmus




Analysis of survey
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


Analysis of survey1
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


On genetic testing
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


Analysis of survey2

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


Recommendations
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



Rods cones vs photoreceptors
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.


Where are the rods
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


Where are the rods1
Where are the rods?

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



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