Lecture 5 and 6 (starting pres 4-end)

Question 1

Which pathway is isolated using a high TEMPORAL frequency? What function does this allow us to obtain?

Answer 1

MAGNOcellular (aka luminance) pathway

-relative luminous efficiency function…plots shifts in the spectrum (normally 555nm) in those w/ CVDs

Question 2

about where does a protanope’s peak wavelength lie on the relative luminous efficiency plot?

• the deuteranope’s?
• the tritanope’s?

Answer 2

protanope: 535nm (no L cones - shifts toward shorter wavelength) - 535 seen brighter, L wavelengths seen darker)
deuteranope: 560nm
tritanope: 555nm (same as normals)

Question 3

for protanopes, how do long wavelengths appear compared to short and medium wavelengths?
-what about for protanomalies?

Answer 3

DARKER

protanomalies - result of intermediate curve b/w nml and dichromatic curve

Question 4

a slow, flickering stimulus isolates which pathway? measures what?

Answer 4

PARVOcellular pathway. Measures detection thresholds

Question 5

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

Answer 5

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

Question 6

Tritanopes can’t discriminate b/w which two wavelengths?

Answer 6

between ~450-480nm (where blue is)

Question 7

T/F: the major axes of trichromats do NOT converge to a single point, as they have a wide range of orientations

Answer 7

true (referencing macadam ellipses w/ different axes in color matching)

Question 8

T/F: the major axes of ANY dichromat do NOT converge to a single point

Answer 8

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

Question 9

T/F: Misreads on Ishihara count as errors

-why (esp w/ Ishihara) might this happen?

Answer 9

FALSE- must be excluded in determining whether a CVD is present (i.e. 3/8, 5/6)

-SERIF font

Question 10

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?

Answer 10

38-plate: 3 errors = defect

24-plate: 2 errors = defect

Question 11

Ishihara: excellent ___ and ___. Are these properties still good w/ HRR plates? When would you use HRR plates instead?

Answer 11

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

Question 12

topic: detection threshold.

- saturation of ZERO produces what color? can two colors been seen as different?

Answer 12

equal energy WHITE - can’t discern until you start to increase saturation

Question 13

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)

Answer 13

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

Question 14

Which type of dichromat has a co-punctal point OUTSIDE the color space

-All these lines converging to a single point are termed what?

Answer 14

deuteranope (point has a negative value)

-color CONFUSION lines (observers CAN’T tell the difference between the colors along that line)

Question 15

which point divides the spectrum into two regions for dichromats?

Answer 15

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)

Question 16

Co-punctal point locations for:
protanopes?
deutanopes?
tritanopes?

Answer 16

(X,Y)

protanope: 0.75, 0.25 (reddish purple)
deutanope: 1.4, -0.4 (bluish purple)
tritanope: 0.17, 0 (violet)

Question 17

how are vanishing plates designed?

Answer 17

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)

Question 18

T/F: the spectral anomaloscope is the ONLY test that can diagnose a CVD fully.

Answer 18

True - PIC plates ID can’t identify, classify, and grade all types of CVD separately - anomaloscope does it all

Question 19

How many plates technically needed for Ishihara for official “diagnosis” (even though it doesn’t diagnose)

Answer 19

16

Question 20

What is a tetartan defect?

Answer 20

Defect of the vis PATHWAY itself - all three cones nml…post-receptoral connexns abnml

Question 21

What is HRR GOOD at?

Answer 21

grading the severity

-considered COMPLIMENTARY to ishihara -suggested to do ishi to schreen, then HRR to classify/grade

Question 22

T/F: the examiner w/ screening plates waits as long as it takes the pt to reply w/ an answer

Answer 22

false - 4 secs and move on. we ain’t got all day buddy..

…but seriously-hesitation IS CONSIDERED and error, may indicate slight CVD

Question 23

What’s unique about the C’s seen in the cambridge color test?

Answer 23

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.

Question 24

hue discrimination tests (farnsworth D15, 100 Hue, LD15) are for more (mild/mod/severe) CVDs

Answer 24

severe

Question 25

will someone with a slight CVD pass the Farnsworth D15?

Answer 25

probably. Forms TWO groups of test subjects: nml-slight CVD (pass) and mod-severe CVD (fail)
- used for vocational testing

Question 26

The desaturated Farnsworth (LD15) detects the ____ of the CVDs (picks up on more subtle ones). Useful in (congenital/acquired) CVDs?

Answer 26

severity

acquired!

-color quality control workers - must be precise

Question 27

Farnsworth 100 Hue will only identify pts w/ ___ and ___ CVDs.

• Do these caps fall on color confusion lines as seen with the D15?
• Where would a CVD subject make mistakes w/ the 100 Hue test?

Answer 27

moderate-severe only

• NO (color confusion lines’ colors would be in different boxes)
• errors where caps are ADJACENT to confusion lines, where confusion lines are TANGENT to the color circle

Question 28

Munsell 100 Hue: typical axes of confusion for:

• protan
• deutan
• tritan

-grading system? (assume no errors exist around specific axes)

Answer 28

protan: 17, 64
deutan: 15, 58
tritan: 5, 45

superior: 100

Question 29

How does the city university test relate to the D15?

• does it detect mild CVDs?
• Do protans or deutans make more errors?
• Can this test grade protans?

Answer 29

uses 4 caps: protan/deutan/tritan color conf lines, and the 4th cap is the next cap color from the D15

• nope: only MODERATE-SEVERE (like d15 etc)
• DEUTANS = more errors (>5 errors =severe deuteranomalous)
• NO - can’t grade protans

Question 30

Anomaloscope - GOLD STANDARD for testing CVDs. Two types: R/G and B/Y: names? Which one can be used for tritan defects?

• In the upper half, ____ is FIXED (try to match it on the bottom)
• in the bottom half, ____ is fixed

Answer 30

Nagal, Neitz, Oculus –> Oculus can be used for tritans

• upper: luminance
• bottom: hue

Question 31

hue mixture field (upper half): 0-73 (546nm-670nm) -which two colors are at these wavelengths?

-how does this relate to the fact that a trichromat imitates a dichromat because of this?

Answer 31

546-pure green
670-pure red

S-cones are NOT sensitive to anything in this range - it’s as though they don’t exist! Only using M and L cones to detect deutan or protan defects!

Question 32

anomaloscope: trichromats act as dichromats (d/t isolation of S-cones), and dichromats act as ___chromats - they only have to change what parameter to get the colors to match?

Answer 32

monochromats - change LUMINANCE only!!

Question 33

so a TRICHROMAT using the anomaloscope must use an appropriate combination of HOW many wavelengths? How about a dichromat?

Answer 33

trichromat: combo TWO wavelengths
dichromat: only ONE wavelength, and they can match it by changing ONLY the luminance value (on the bottom)

Question 34

The anomaloscope uses what fxn to classify whether a pt is a protanope or deutanope?

Answer 34

relative luminous efficiency

• if pt is a PROtanope, they’ll DIM the luminance of the middle wavelength (dim the YELLOW) (b/c they see the longer wavelength as DIMMER and want to match it w/ the middle wavelength)
• deutanopes will set the luminance value close to NORMAL (since their color vision is pretty close to nm) - nml luminance value ~17

Question 35

What does the Moreland equation measure?

Answer 35

B/Y defects. Don’t need to memorize the formula

Question 36

Can lanterns be used to identify CVDs?

Answer 36

NO- only to tell whether the observer can tell the two colors apart (maritime, military, avation)

Question 37

Among the following options, who is most likely to FAIL the lantern test: protanomalous, deuteranomalous, or dichromats?

Answer 37

DICHROMATS (need 3 opsins to discern the difference) -

-anomalies may pass the test - unfortunately, only 75% sensitivity means that 25% of pts will PASS the Farnsworth lantern

Question 38

Three causes of ACQUIRED CVD?

Answer 38

1) systemic pathology
2) intracranial injury
3) therapeutic drugs

-interesting = acquired might be MONOcular or BINOcular, and also might be SECTIONAL depending on where they affect the retina

Question 39

acquired CVDs usually present w/ reduced visual ___ and visual ____

• more likely to be what type of defect?
• preference b/w males and females?

Answer 39

reduced visual acuity and visual field

• usually TRITAN defect
• equal prevalence males/females

Question 40

According to Kollner’s rule, are B/Y or R/G more likely to change first? Based on the principle that what part of the eye is affected first?

Answer 40

B/Y FIRST (inner retina)

R/G LATER (optic nerve)
-Note: important: R/G actually noticed MORE

Question 41

all of the following can produce an acquired CVD:

Answer 41

DM, Gl, AMD, MS, CSR (central serous), alcoholism (competitive inhibition in liver for conversion to 11-cis retinal), leukemia, sickle cell, dominant optic atrophy

Question 42

Name 4 drugs that can cause a CVD:

-which test becomes IMPORTANT when you have a pt taking these drugs?

Answer 42

• Digoxin, Ethambutol (both deutan)
• Chloroquine/thioridazine (blue)
• Viagra, Vitamin A deficiency (blue)

FM-100 Hue test (score would keep increasing above 100 if defect is present)

Question 43

Define:

• color agnosia:
• color anomia:
• cerebral achromatopsia:

Answer 43

agnosia: can’t assc color w/ object
anomia: can’t NAME color (can see them no prob)
achromatopsia: V4 lesion

Question 44

What’s the main factor in color vision alteration produced by aging changes?

Answer 44

increased LENS density (absorption of short wavelengths)

Question 45

Name a few occupations with ESSENTIAL trichromatic CV:

Answer 45

military, aviation, electricians, cops, navigation (fishermen, pilots), color matchers (textile workers)