5) Anomalies Color vision

Provide examples of two inherited colour defect.

1. Red-green anomalies (X-linked recessive)

   • Men 0.8%; woman 0.4%

2. Tritan (autosmal dominant)

What are the prevalence of the different color vision defects?

What are the Societal Implications of Anomalous Colour vision?

• not physically debilitating

• some may not be aware

  • learn they have it after FAILING a color vision test

List occupations related to public safety that have color vision standards.

• Airline Pilot, Firefighter

• US custom & border protection

• USDA meat inspector (Ishihara)

List occupations where normal colour discriminations can be an advantage.

• Chemical or electrical engineering

• Pharmacy

• Optometry

• Ophthalmology

• Dentistry

• Surgery

• Videographer

How do red–green color anomalies affect color perception?

→ Difficulty distinguishing dark or desaturated (pastel) colors that lie along red–green confusion lines

• 💡 Brighter light improves color discrimination and color naming

Do colored SUNGLASSES interfere with the ability of patients with inherited anomalies to quickly and correctly identify colored traffic signals?

Yes

• certain non-neurtal tins (except Gray) make it harder to see traffic light

• ppl with anomalous defects (eso protons seeing red) shouldn’t wear it

What does Photopic luminosity curve receive it’s input from?

2-3 LWS : 1 MWS (no input from SWS cones)

How do protanopes and protanomalous trichromats perceive red lights?

→ severe loss of luminosity to RED LIGHTS sensitivity, perceiving red as dim or dark

.

Such as:

• brake lights → delayed rxn times

• red traffic lights

• red surface → looks black

• emitting Diode

• laser pointers

How do deuteranopes & deuteranomalous trichromats perceive red lights?

No loss of luminosity

Why should color vision testing be done at a young age?

→ Provides baseline color vision data early in life (helpful for careers)

• parents and teachers should be informed about child’s color vision status

• Parents counselled about career choices

Write the Male and Female phenotypes.

XY - Male

XY -Anomalous Male

XX - Female

XX - Carrier Female

XX - Anomalous Female

What genes does the X-chromosome have?

1 L-cone opsin gene

1+ M-cone opsin genes

What are the genetic causes of color vision deficiencies?

Intergenic (between genes):

• Normal color vision

• Dichromacy

.

Intragenic (within genes):

• Normal color vision

• Dichromacy

• Anomalous trichromacy → caused by a hybrid gene (basis of abnormal cone photopigment)

What are Acquired color vision anomalies?

→ 2er to disease or toxicity

• either Red–Green or Blue–Yellow

• unilateral or asymmetric

Must be assumed that any in the color vision of the two eyes as demonstrated on a color vision test…

due to an Acquired Anomaly

What is Achromatopsia?

→ where have manifests monochromatic vision

• fully expressed at birth

What is Autosomal Recessive (AR) Achromatopsias? Mention the 2 types, signs + sx, and treatment.

1. Complete (AR) Achromatopsia → only Rods are present

2. Incomplete (AR) Achromatopsia → residual L/M cone function

• common

.

Signs + sx

• No or very poor Color discrimination

• Nystagmus

• Photophobia

• VA~20/200

.

Treatment

• Dark red lenses (minimizes rhodopsin bleaching) for bright light conditions

What is X-linked (XL) Achromatopsias? Mention the 2 types, signs + sx, and treatment.

→ aka Blue or S cone monochromacy (have only Rods & S cones)

.

Signs + sx

• similar to AR Achromatopsia

.

Treatment

•  Magenta colored lenses 

What is Cone Monochromacy?

• monochromatic color matching

• VA = normal

• defect in postreceptoral processing of color info

Where does retinal achromatopsia occur?

Retina

Where does cerebral achromatopsia occur?

Extrastriate Cortex

What is Chromatopsia?

→ NOT TRUE color vision anomalies b/c they don’t cause a ↓ ability to discriminate colors

• represent “distortion” of color vision

List 2 common causes of Chromatopsia.

1) Cataract extraction → Blueness perception (Cyanopsia)

2) 2er to drugs/medications → Yellowness perception (Xanthopsia)

• Digitalis (yellow vision)

• Fluorescein in Fluorescein Angiography

What is Synesthesia?

→ neurological phenomenon where stimulating ONE sensory/cognitive pathway → automatic, involuntary experiences in a 2^nd sensory/cognitive pathway

• Cause: abnormal link between diff cortical modules

• e.g., GREEN whenever someone’s presented with the number “5,”

What is Chromesthesia?

→ associating SOUNDS with colors

• common form of synesthesia

• ppl tend to have perfect pitch

What is Köllner’s rule?

Outer retinal disease, Media changes → Blue–Yellow anomalies

Inner retina, Optic nerve, Visual pathways, Visual cortex → Red–Green anomalies

Post receptoral lesions → Blue–Yellow & Red–Green anomalies

How can acquired color defects change as eye disease progresses?

• Early disease may cause a blue–yellow defect → progress to red–green defect

  • Some diseases can show the reverse pattern

• Severe disease may cause nonselective color loss (loss of multiple color pathways)

What is color vision testing is based on?

knowledge of confusion lines

List the Goals of CV Testing.

• Screening – i.e. Congenital versus Acquired

• Diagnosis – i.e. type and severity

• Vocation or Occupational testing

Who will have greater  occupational consequences? Protans, Deutan or Tritans?

Protan

What do red–green vs blue–yellow acquired color defects indicate?

Red–green defects = cone and optic nerve disease

Blue–yellow defects = retinal and choroidal disease

Give examples of Pseudoisochromatic (PIC) plate tests.

1. Ishihara

2. HRR

3. CVTME

Give examples of Arrangement tests.

→ color cap tests

1. Farnsworth-Munsell 100

2. Panel D-15

3. Lanthony Desaturated D15

Give examples of Matching tests.

1. Anomaloscopes

2. C100

3. CUT

Give examples of Naming tests.

Vocation/occupations (Lantern tests)

Give examples of other occupational Color tests.

Rabin Cone Contrast Test

What are PIC plates?

→ Patterns of objects, letters or numbers placed on isoluminant bg

• Figures usually fall along the dichromatic confusion line

  • Normals = identify chromatic differences

  • CVD = will have difficulties

• DON’T distinguish between Dichromats & anomalous trichromats

• CAN distinguish between Protan and Deutan

List the 7 different PIC plate types.

1. Demonstration

2. Disappearing (vanishing)

3. Diagnostic

4. Ambiguous or alteration (transformation)

5. Combination

6. Quantitative

7. Hidden-digit

What is Demonstration plate?

→ plate luminous reflectance cues and/or color differences that don’t lie on confusion line

• you don’t need color vision for a correct response

• helps demonstrate how the test symbols look

• helps pick up malingerers (pretends or exaggerates incapacity)

• e.g., Ishihara & HRR Demo Plates

What are Disappearing plates?

→ target/stimulus is defined by a color difference from the bg that straddle confusion lines

• Object is invisible to those with certain color deficiencies

• helps detect color deficiencies but not distinguish them

• (-) Slower to administer for CVD

• (-) Frustrating for color defectives to repeatedly see ‘blank’ plate

What are Ambiguous or Alteration (Transformation) plates?

→ helps provide an alternate response for the color vision defectives

• has colours that can be confused with the bg and others that are not

  • Normal color vision: see one thing

  • Color deficiency: see another thing that’s just slightly altered

• helps confirms that the test is understood

• (+) prevents the frustration found with blank plates

What are Combination plates?

→ incorporates disappearing and demonstration figures

• Color normal = might see 2 figures

• CVD = sees 1 figure

What are Diagnostic plates?

 → Multiple disappearing plates for different CVD

• have 2 figures

  • Normals: should see 2 & 6

  • Deutan = see 2

  • Protan = see 6

What are Quantitative plates?

→ set of plates with increasing color difference

• Confusion with small color difference = Mild

• Confusion with large color difference = Moderate/Severe

▪ e.g., Hardy-Rand-Rittler (HRR)

What are Hidden-digit plates?

→ Opposite of a disappearance test

• Visible only to those with CVD, normals should see nothing

d see 5

What defects can Ishihara vs HRR test detect?

Ishihara (Sensitive) = Protan & Deutan defects

HRR (Sensitive) = Protan, Deutan, Tritan & severity

What is the Ishihara PIC test? Mention the plates used.

→ figures on each plate have a random pattern of variably-sized dots → figures & bg lie close to confusion lines

• DOESN’T distinguish between Dichromats and Anomalous trichromats, it only differentiates b/w protan vs deutan

• (+) ↑ sensitivity & specificity (close to 1.0)

• (+) useful in children >5 years

• (+) can perform under diff illumination

Plates = demonstration, disappearing, diagnostic plates, alteration & hidden

Why is an Ishihara “disappearing plate” not seen by both protans and deutans?

• figure and bg colors are chosen to fall along red–green confusion lines

  • little color difference b/w protans and deutans in this region of color space

  • protans and deutans confuse the figure with the background, causing the figure to “disappear”

What is the “cut-off” for normal vs deficient colour vision in Ishihara PIC test

13+ = Normal

<9 = deficient

Although the Ishihara test as a whole performs "very close to 1" in both Sensitivity and Specificity, what does it have the tendency to do?

PASS: Very Mild Deutans

FAIL: Some Normals 

List the 6 shortcomings of Ishihara (compared to HRR).

1. No TRITAN plates

2. Doesn’t provide a severity diagnosis

3. Relatively mildly affected CVDs (Protanamalous, deuteranomalous) may make as many errors like dichromats (Protanopes, deuteranope)

4. Can be memorized

5. Hard to administer in children younger than 5 years.

6. Doesn’t distinguish b/w Dichromats and Anomalous trichromats (i.e., protanope from protanamalous, deutaranope from deuteranomalous)

List the Common Mistakes in the Interpretation of the Ishihara.

1. Using the wrong failure criterion → misdiagnosis

2. Assuming that patients who make many errors have a “severe” CVD

   • # of errors on the Ishihara test is NOT a measure of severity, except that a very small number of errors may indicate a mild CVD

3. Diagnostic plates to differentiate Protan and Deutan CVD, don’t ALWAYS yield a diagnosis.

   • 30 to 40 % of cases diagnosis is wrong

How many Hardy-Rand Rittler (HRR) Color test plates are there?

Plates = Demonstration, Diagnostic & Screening plates

• Demonstration plates = 4 plates

• Diagnostic Plates = 14 plates (10 = Red-Green, 4= Blue-Yellow)

• Screening Plates = 6 plates (2=Blue-Yellow, 4= Red-Green CVD)

List the advantages of HRR test.

• Has Tritan screening & diagnostic plates

  • have target that lie on the “Tetartanopia” confusion locus but this doesn’t exist

• Doesn’t discriminate Dichromacy from Anomalous Trichromacy

• Classifies Protan, Deutan, Tritan & severity

• Used on very young childre b/c it uses symbols (circle, triangle, cross)

How do you diagnose normal vs defective colour vision using the HRR color test?

Normal

• All 6 screening plates

• 1+ errors in the screening plates but 0 in the subsequent diagnostic plates

.

Red-Green Deficiency

Protan = Protan column > Deutan column

Deutan = Deutan column > Protan column

Unclassified = Protan column = Deutan column OR errors in screening plates

.

Blue-Yellow Deficiency

Tritan = Tritan column > Tetartan column

Tetartan = Tetartan column > Tritan column

Unclassified = Tritan column = Tetartan column OR errors in screening plates

What does extensive scattered errors throughout the various groups of plates on the HRR test may indicate?

Any of the following:

• Malingering

• Monochromatism (total color blindness)

• Low color discrimination approaching monochromatism

How woud you classify someone as being Red-Green Deficiency on the HRR color test?

Last error in plates 7-10 or 11-15 + no errors in 16-20 = MILD

Last error in plates 16-18 + no errors in plates 19-20 = MEDIUM

Last errors in plates 19-20 = STRONG

How woud you classify someone as being Blue-yellow Deficiency on the HRR color test?

Last error in 5-6 + no errors in 21-24 = MILD

Last error in 21-22 + no errors in 23-24 = MEDIUM

Error in 23-24 = STRONG

For those who were classified as MILD on the HRR test, what was their Farnsworth D15 test vs Anomaloscope scores?

Farnsworth D15 test = PASS

Anomaloscope = <30

True or False - Not all Dichromats (Protanope/Deuteranope) were correctly classified as 'STRONG'.

True

What is the Holmgren Wool Test?

→ earliest arrangement tests where subjects are asked to sort colours into sequences/groups

• Colors have the

  • ✅ Same Munsell values and Chroma

  • ❌ Different Munsell Hue (R, Y, G, B, P)

What is the Farnsworth Munsell 100 Hue?

• 100 caps with colored papers (15 removed to create JND)

• Total Error Score (TES) plotted in score sheet

• Doesn’t distinguish dichromacy from anomalous trichromacy (i.e Protanope vs Protanomalous)

• Time consuming (rarely used)

What does the Error Score (TES) indicate for FM 100 test?

severity of defect

What does the midpoint indicate for FM 100 test?

type of color vision defect

What midpoint values would indicate the different color defects?

What are the typical axis of confusions in FM 100 Hue test?

What type of color defect will someone who has diabetic retinopathy have?

Tritan

What type of color defect will someone with Retrobulbar Neuritis associated with MS have?

Recovery from Red-Green defect

What is the function of Farnsworth D-15/Dichotomous D-15/Panel D-15/Regular D-15?

→ distinguish the functionally color blind from the Moderately color defective and the normal” (hence called dichotomous)

• used to evaluate Acquired color vision defect

• discriminates Protan, Deutan & Tritan defects, but NOT discriminate between Dichromacy and Anomalous trichromacy

• has low sensitivity - some subjects with Mild defects (anomalous trichromacy) may pass the test

What is a pass vs fail in Farnsworth D-15?

• PASS = ‘mild’ CVD (normals + mildly CVD can complete this test)

• FAIL = ‘moderate-to-severe’ CVD (2+ crossings)

True or false -  Those who pass the Farnsworth D15 test have a mild deficiency that is unlikely to cause significant handicap in everyday color tasks.

False - they might still have trouble with everyday color tasks

What does the spacing of colors alongs confusion lines allow for?

Makes it easy to:

• Pass normal trichromats and many anomalous trichromats

• Fail all dichromats

A Young male Fails the Ishihara Color Plate Test but PASSES the Farnsworth D-15 arrangement test. What does this indicate?

Who typically fails both the Ishihara and Farnsworth D-15 tests?

• Protanopes

• Deuteranopes

• Severe (extreme) anomalous trichromats (nearly dichromatic)

What is the Lanthony Desaturated D15 test?

→ identical to the Farnsworth D-15 test, except the color caps are much less saturated than D-15

• detects Anomalous trichromacy (Sensitive test), mild Acquired CVD (e.g.,Cataract or Glaucoma)

• needs lots of light (600-800 lux)

What is the Farnsworth Lantern (FaLant)?

• 2 light lantern for US Navy, with Red, Green and White

• No longer commercially available

What is the Stereo Optical OPTEC 900?

• No longer commercially available

• Used in US Military, FAA

What is the Gold Standard for color vision testing for the US Air Force?

 Rabin Cone Contrast Test (CCT)

What is the Rabin Cone Contrast Test (CCT)?

1) Detects Cone deficiency severity + Congenital CVD

• measures the severity of cone function loss

• tracks cone function over time

• helps in disease detection + monitor progression

• monitor treatment efficacy

2) Detect and monitor Acquired CVD

• AMD

• TBI

• Parkinson’s

• GLC

• Diabetic retinopathy

• MS

• Retinal Toxicity due to High Risks meds such as Plaquenil

What is the Nagel Anomaloscope?

→ Only Clinical Instrument that can provide a complete diagnosis of congenital CVD

• Anomalous Trichromats from Normal Trichromats

• Dichromats from Anomalous trichromat

• ⭐ standard

What is the mixture field and test field?

→ observer is asked to match the mixture filed to the test field

.

MIXTURE FIELD (upper-half)

• RED and GREEN wavelengths

• mixture scale setting 0-73 represent various combinations of 546 (Green) to 670 nm (Red)

.

TEST FIELD (lower half):

• fixed YELLOW test field (590 nm)

• test field knob setting 0-35 varies test field YELLOW Brightness/Luminance

True or False - A person with normal trichromacy can match the test field to the appropriate mixture field?

True - b/c they’re dichromatic

True or False - A person with dichromacy (protanope/deuteranope) can match the test field to the appropriate mixture field?

Yes, no matter what combo of 546 and 670 nm is present in the MIXTURE FIELD

• Reason: b/c from approximately 545 to 700 nm, Red–Green Dichromacy pt have only ONE photopigment and manifest MONOCHROMATIC VISION

 If the TOP MIXTURE FIELD is set to pure 546 nm, can a patient with Red–Green Dichromacy [Protanope/Deuteranope] adjust the mixture field?

If the TOP MIXTURE FIELD is set to pure 670 nm, can a patient with Red–Green Dichromacy [Protanope/Deuteranope] now adjust the wavelength of the test field so that the two fields appear identical?

How do protanopes and deuteranopes differ on the Nagel anomaloscope?

→ Both protanopes and deuteranopes can match any red–green mixture (0–73) to the test field

• Deuteranopes: Use the same test field setting because brightness remains constant

• Protanopes: Adjust the test field brightness (dimmer for red, brighter for green) because red appears dimmer due to ↓ long-wavelength sensitivity

  • their luminance function is displaced towards shorter wavelengths

How can the MIXTURE SCALE SETTING distinguish protanomalous from deuteranomalous?

Deuteranomaly - may require more 546 nm (Green) in the MIXTURE FIELD due to displaced M-cone (the mixture looks more red to them) → adjust MIXTURE scale between 0-40

Protanomaly - may require more 670-nm (red) in the MIXTURE FIELD due to displaced L-cone (the mixture looks more green to them) → adjust MIXTURE scale between 50-73

How can the TEST FIELD (BRIGHTNESS) SETTING distinguish protanomalous from deuteranomalous?

Deuteranomaly - has the same luminosity function as normal CVD → adjust TEST FIELD scale to 17

Protanomaly - has the luminosity function similar to protanope → adjust TEST FIELD scale to less than 17 (b/c mixture field already appears dim to them?

How do anomalous trichromats (deutranomolous, protanomalous) perform on color matching tests compared to normal trichromats and dichromats?

Less specific (wider range of matches) than normal trichromats

More specific (narrower range of matches) than dichromats (protanope, deutranope)

What equation is the gold standard ⭐ for diagnosing the FOUR major X-linked color defects?

Rayleigh equation

What is the Rayleigh equation used for?

→ protan/deutan

Red + Green ≡ Yellow

What is the Moreland equation used for?

→ tritan

Blue + Green ≡ Blue-Green

What does trouble with BY defect include?

1. Macular pigment

2. Crystalline lens variability

What is the Medmont C-100?

→ Flicker matching (rapid alternation) of Red (650) and Green (560) using dual light emitting diode

• Subject controls luminance ratio of Red and Green

• Reliably distinguishes

  • ✅ Protans from normal

  • ❌ Deutans from normal

What is the City University Test (CUT)?

→ MATCHTING TEST that invovles matching the Central Hue with one of the Peripheral Hue (which appears similar)

• forced choice procedure test

• derived from the colors of the D-15

• 5 hues

  • 1 test hue

  • 1 hue = adjacent D-15 hue

  • 3 hues = Protan, Deutan & Tritan confusion loci

What is the SWAP [Short Wavelength Automated Perimetry]?

→ detects early GLC by isolating S-system function

• S cone (blue-yellow pathway) is vulnerable to GLC

• Stimulus = Short wavelength (to maximize S cone sensitivity)

• Background = yellow (to SUPPRESS (adapting) L & M cones)