1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

The Nagel Anomaloscope

Discussion in 'Ask A Flight Surgeon' started by RS1, Dec 1, 2008.

  1. RS1

    RS1 Well-Known Member

    Joined:
    Sep 2, 2008
    Messages:
    131
    Likes Received:
    8
    I've read some documentation about this test and am confused as to what results are consider as passing. I know it's not an FAA acceptable test, but it gives you more information about yourself. My question is: Is no match at all a passing score? The documentation I read mentions that some people are "fooled" into thinking certain red and green mixtures are identical to certain yellow hues... So is this saying that there really can't be a match between the 2 sides for a normal person?

    Thanks
  2. My Flight Surgeon

    My Flight Surgeon Sr. Aviation Medical Examiner Staff Member

    Joined:
    Aug 14, 2006
    Messages:
    4,806
    Likes Received:
    118
    This test is over 100 years old and no one knows much about it any longer. I have never seen it performed.
  3. RS1

    RS1 Well-Known Member

    Joined:
    Sep 2, 2008
    Messages:
    131
    Likes Received:
    8
    Maybe I got the wrong anomaloscope? This was administered to me by a college professor when I went to an optometry college to take the FALANT...
  4. RS1

    RS1 Well-Known Member

    Joined:
    Sep 2, 2008
    Messages:
    131
    Likes Received:
    8
    Here is a write up on the test...:

    1
    Vision Science II - Monocular Sensory Aspects of Vision​
    Lecture 34 – Anomaloscope​
    THE NAGEL ANOMALOSCOPE​
    Refer to notes for the previous lecture.​
    Summary – normal trichromat​
    • ​
    The anomaloscope helps diagnose red-green dichromacy and red-green anomalous trichromacy.

    • ​
    It performs a 3-hue color matching experiment (two pure spectral hues mixed to match a third).
    Specifically, 546-nm green and 670-nm red are mixed to match 590-nm yellow

    • ​
    In this range of wavelengths, trichromats are actually dichromatic.

    • ​
    A normal trichromat (dichromat in this range) can achieve a metameric match with three hues, but not
    with two. You cannot fool them into thinking that two different hues are the same color, no matter how
    you adjust their brightnesses. That is, neither the 546-nm nor the 670-nm lights will ever match the 590-
    nm light.

    Diagnosing dichromacy​
    • ​
    Over the range of wavelengths used, a person with red-green dichromacy is monochromatic.

    • ​
    These patients will be able to achieve a metameric match with two hues. You can fool a protanope into
    matching either a 546-nm or 670-nm light to a 590-nm light by adjusting their relative brightnesses. A
    deuteranope can also be fooled into incorrectly matching those hues with 590-nm.

    Differential diagnosis of protanopia versus deuteranopia​
    • ​
    You can differentiate between protanopes and deuteranopes based on the way they adjust the
    brightness setting.

    • ​
    Recall that the protanope’s V(λ) function is abnormal, but the deuteranope’s V(λ) function is normal.

    • ​
    The 670-nm light will appear dimmer than normal for the protanope. The 546-nm light will appear
    brighter than normal for the protanope.

    • ​
    Therefore, when matching 670-nm light to 590-nm, the protanope will set make the test light (590-nm)
    dimmer than normal.

    • ​
    When matching the 546-nm light to 590-nm, the protanope will make the test light (590-nm) setting
    brighter than normal.

    • ​
    If the brightness settings are normal, the dichromat is a deuteranope.

    Anomalous trichromats​
    • ​
    Protanomalous and deuteranomalous trichromats make close-to-normal settings for both the mixture and
    brightness.

    • ​
    Since they are not dichromats, they will not be fooled into matching pure 546-nm light or pure 670-nm
    light with 670-nm light. However, their mixture setting will be slightly incorrect compared to trichromats.

    • ​
    Consider deuteranomalous trichromats as being “green-weak.” To compensate, they will tend to add
    more green to the mixture than normal.

    • ​
    Consider protanomalous trichromats as being “red-weak.” To compensate, they will tend to add more
    red to the mixture than normal.

    • ​
    As described above, protans (including protanomalous trichromats) will make abnormal brightness
    settings. This also helps to differentiate between protanomalous versus deuteranomalous trichromats.
    Q. Explain Schwartz Fig. 6-16.
    Example question from the Optometry Exam Review Book:
    Question #2. A color-deficient person looks in an anomaloscope and does not accept a color-normal’s
    match? The nature of the person’s deficiency is:
    a. protanomaly
    b. deuteranopia
    c. protanopia
    d. tritanopia

    2​
    11. A patient mixes monochromatic green and red lights to obtain a metameric match with
    monochromatic yellow. If the he thinks any red-green mixture looks the same hue as the yellow light,
    which of the following diagnoses is/are possible?
    a. protanomaly
    b. protanopia
    c. deuteranomaly
    d. deuteranopia
    e. none of the above
    12. In addition to the adjustment described in Question 11, assume that the patient reduces the radiance
    of the yellow light below normal when the mixture setting is pure red, and increases the radiance above
    normal when the mixture is set to pure green. Which of the following diagnoses is/are possible?
    a. protanomaly
    b. protanopia
    c. deuteranomaly
    d. deuteranopia
    e. none of the above
    13. For which of the following anomalies would the patient accept normal mixture and luminance
    settings?
    a. protanomaly
    b. protanopia
    c. deuteranomaly
    d. deuteranopia
    e. none of the above
    14. Suppose the mixture setting contains a slightly greater-than-normal amount of green but the
    luminance setting is normal. He probably has ...
    a. protanomaly
    b. protanopia
    c. deuteranomaly
    d. deuteranopia
    e. none of the above
    15. Suppose the mixture setting contains a slightly greater-than-normal amount of red but the luminance
    setting is significantly greater than normal. He probably has ...
    a. deuteranomaly
    b. deuteranopia
    c. protanomaly
    d. protanopia​
    e. none of the above



Share This Page