Lecture 5 and 6 (starting pres 4-end) Flashcards
(45 cards)
Which pathway is isolated using a high TEMPORAL frequency? What function does this allow us to obtain?
MAGNOcellular (aka luminance) pathway
-relative luminous efficiency function…plots shifts in the spectrum (normally 555nm) in those w/ CVDs
about where does a protanope’s peak wavelength lie on the relative luminous efficiency plot?
- the deuteranope’s?
- the tritanope’s?
protanope: 535nm (no L cones - shifts toward shorter wavelength) - 535 seen brighter, L wavelengths seen darker)
deuteranope: 560nm
tritanope: 555nm (same as normals)
for protanopes, how do long wavelengths appear compared to short and medium wavelengths?
-what about for protanomalies?
DARKER
protanomalies - result of intermediate curve b/w nml and dichromatic curve
a slow, flickering stimulus isolates which pathway? measures what?
PARVOcellular pathway. Measures detection thresholds
Topic: wavelength discrimination
-Which two wavelengths show OPTIMAL wavelength discrimination in a normal trichromat? i.e. where’s the MINIMA of the wavelength discrim. fxn?)
- Where is the optimum for pro/deutanopes?
- Wavelengths longer than ___nm can’t be discriminated in pro/deutanopes
trichromat: 500nm, 600nm (MOST sensitive to small changes in wavelengths at these wavelengths)
pro/deutanope: 495 (close)
-can’t discriminate above 540nm (where green starts)
**wavelength discrimination SEVERELY IMPAIRED in protanopes and deuteranopes
Tritanopes can’t discriminate b/w which two wavelengths?
between ~450-480nm (where blue is)
T/F: the major axes of trichromats do NOT converge to a single point, as they have a wide range of orientations
true (referencing macadam ellipses w/ different axes in color matching)
T/F: the major axes of ANY dichromat do NOT converge to a single point
FALSE - they DO converge to a single point - aka co-punctal points. They DON’T converge for a nml trichromat, giving them their excellent color discrimination
T/F: Misreads on Ishihara count as errors
-why (esp w/ Ishihara) might this happen?
FALSE- must be excluded in determining whether a CVD is present (i.e. 3/8, 5/6)
-SERIF font
how many errors on the first 16 plates of the 38-plate ishihara is considered a defect?
how about on the first 12 plates of the 24-plate edition?
38-plate: 3 errors = defect
24-plate: 2 errors = defect
Ishihara: excellent ___ and ___. Are these properties still good w/ HRR plates? When would you use HRR plates instead?
Ishihara: high sensitivity, and specificity (won’t miss anyone)
HRR - will miss 10% of CVDs…used for B/Y defect suspicion, OR for QUANTIFYING the type of defect
topic: detection threshold.
- saturation of ZERO produces what color? can two colors been seen as different?
equal energy WHITE - can’t discern until you start to increase saturation
An observer is shown a spot, then the chromaticity is changed around that spot and the observer says the second spot looks like the first. Where must this second spot be relative to the first?
-observers have a good ability to see changes in the __/__ region of the color space, but a poor ability in the ___ region (recall: variability)
within the same MACADAM ellipse.
-each ellipse has a major AXIS, and each axis has a WIDE range of orientations (around 180 degrees)
- GOOD: blue/purple
- POOR: green
Which type of dichromat has a co-punctal point OUTSIDE the color space
-All these lines converging to a single point are termed what?
deuteranope (point has a negative value)
-color CONFUSION lines (observers CAN’T tell the difference between the colors along that line)
which point divides the spectrum into two regions for dichromats?
the neutral point. Pro/deutanopes’ neutral point separates B/Y (since that’s all they can tell the difference between), and tritanopes neutral point separates (R/G)
Co-punctal point locations for:
protanopes?
deutanopes?
tritanopes?
(X,Y)
protanope: 0.75, 0.25 (reddish purple)
deutanope: 1.4, -0.4 (bluish purple)
tritanope: 0.17, 0 (violet)
how are vanishing plates designed?
background and number spots all fall on the same color confusion line; can’t be discerned as separate if CVD present. Amt of saturation = severity of defect (recall: MORE saturation=FARTHER from the color confusion line)
T/F: the spectral anomaloscope is the ONLY test that can diagnose a CVD fully.
True - PIC plates ID can’t identify, classify, and grade all types of CVD separately - anomaloscope does it all
How many plates technically needed for Ishihara for official “diagnosis” (even though it doesn’t diagnose)
16
What is a tetartan defect?
Defect of the vis PATHWAY itself - all three cones nml…post-receptoral connexns abnml
What is HRR GOOD at?
grading the severity
-considered COMPLIMENTARY to ishihara -suggested to do ishi to schreen, then HRR to classify/grade
T/F: the examiner w/ screening plates waits as long as it takes the pt to reply w/ an answer
false - 4 secs and move on. we ain’t got all day buddy..
…but seriously-hesitation IS CONSIDERED and error, may indicate slight CVD
What’s unique about the C’s seen in the cambridge color test?
three different chromaticities fall on the protan/deutan/tritan color confusion lines
- pt must identify where GAP is
- uses a COMPUTER screen - expensive. research purposes only.
hue discrimination tests (farnsworth D15, 100 Hue, LD15) are for more (mild/mod/severe) CVDs
severe
