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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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