Color vision

Presented by

K.Eswar ,12immo14.

Today’s Goals :

1.color and color vision .

2.Normal color attributes.

3.Color blindness .

4.Color vision tests.

5.Management of color blindness.

What is color and color vision ?

o Color is the visual perceptual property…

o Color vision is the property of eye discriminating different

colors excited by different wavelengths of light .

o Cones are responsible for the color vision .

o 6 – 7 millions in number .

o Good reactants in photopic condition.

cone Cone cells type

cones can be divided into "red" cones (64%), "green" cones (32%), and "blue" cones (2%) based on measured response curves .

Distribution of color vision represent cell in Retina

Extend 20-30 degrees from fixation point

Processing and transmission of color vision signals :

o Action potential created in photoreceptors

o Bipolar and Horizontal cells

o Ganglion and Amacrine cells .

Color attributes :

Hue : Identification of color , spectral color is determined by the particular wavelength of light

Brightness : Intensity of color, it depends on the luminosity of the component wavelength

In photopic vision-peak luminosity function at approximately 555 nm and in scotopic vision at about 507 nm.

o Saturation :it refers to degree of freedom to dilution with white.

It can be estimated by measuring how much of a particular

wavelength must be added to white before it is distinguishable from white.

The more the wavelength require to be added to make the discrimination, the lesser the saturation.

Color Blindness :

Color blindness is also called “Daltonism”

Defective perception of color -anomalous and absent of color perception is anopia

It may be- Congenital

Acquired

Types of color blindness :

Monochromacy --Total color blindness -- when two or all 3 cone pigments are missing [ very rare ]

A] Rod monochromacy B] Cone monochromacy

Dichromacy - When one of the 3 color pigment is absent

1. Protanopia - RED retinal photoreceptors absent [Hereditary, Sex linked, 1% ]

2. Deuteranopia -GREEN retinal photoreceptors absent [ Hereditary, Sex linked ]

3. Tritanopia -BLUE retinal photoreceptors absent

o Trichromacy :

[Anomalous Trichromacy] Color vision deficiency rather than loss

1. Protanomaly : RED color deficiency [Hereditary, Sex linked, Male1%, ]

2. Deuteranomaly :GREEN color deficiency[Hereditary, Sex linked, Male 5% ]

3. Tritanomaly :BLUE color deficiency [ Rare,Not hereditary ]

Tests for color vision Screening tests.

Grading tests.

Classifying tests.

Vocational tests.

Color vision and principle function

Psudoisochromatic plate test :

Most commonly used tests,

Easily and rapidly administered.

Designed to screen for the presence of red-green inherited color vision defects.

1. Ishihara Plates

2. American Optical Hardy-Rand-RittlerPlates

3. Standard Pseudoisochromatic plates

4. City University test

Ishihara plates :

Comes in three different forms: 16 plates, 24 plates, and 38plates.(10th edition)

Plates should be held at 75 cm under good illumination .

Numerals should be answered in not more than 3 sec

Pathway tracing should be completed within 10 sec.

Designed in four ways

1st plate-

for demonstration and malingerers

Transformation plate:

2-9 plates

A number seen by a color normal appear different to color deficient subject.

Vanishing plats :

Plate no. 10-17th

A number is seen by a color normal but cannot be seen by a color deficient subject

o (18-21)plate-Hidden-digit plates:

normal person does not see a figure

o (22-25)plate-Diagnostic plates:

seen by normal subjects.

Out of initial 21 plates, if 17 or more plates are read correctly by an individual his color sense should be recorded as normal.

If 13 or less plates are correctly read then the person has a red-green color defect.

Plates 22 to25 are for differential diagnosis of Protans and Deutans.

Disadvantage of this test is that it neither test for tritanope nor grade the degree of deficiency

American optic hardy rand ritter There are plates with paired vanishing designs

Contain geometric shapes (circle, cross and triangle)

Shape is in neutral colours on a background matrix of grey dots.

Six plates for screening (four red-green and two tritan),

10 plates for grading the severity of protan and deutandefects

Four plates for grading tritan defects

Ideal for paediatric testing of congenital colour blindness

CITY UNIVERSITY COLOR VISION TEST

10 Plates ,35 cm,daylight,right angle.

Where a centre colored plate is to be matched to its

closest hue from four surrounding color plates.

Three peripheral colors are typical isochromatic

confusions with the central color in color deficiency.

The fourth color is an adjacent color in the D15

sequence and is the intended normal preference

Identifies moderate and severe color deficiency only

FARNSWORTH- MUNSELL 100 HUE TEST:

o Very sensitive reliable and effective method of determining color vision defect.

o The test consists of 85 movable color samples arranged in four boxes of 22 colors

o Subject has to arrange 85 color chips in ascending order.

o The color vision is judged by the error score.

The results are recoded in a circular graphThe Farnsworth-Munsell Hue Test Scoring Software has been developed to speed up and simplify scoring of the FM 100 Hue test and to provide a powerful set of analytical and administrative tools

FARNSWORTH- MUNSELL D-15 HUE TEST –

Abridged version

Patients are asked to arrange 15 colored caps in sequential order based on similarity from the pilot colur cap

Intended for screening color vision defects only.

Used to detect color vision defects such as red-green and blue-yellow deficiencies as opposed to color acuity.

Spectral anamaloscope

Accepted as the most accurate for diagnosis

unlike most other tests,they require a fair amount of skill on the part of the examiner.

1. Nagel anomaloscope

2. Oculus HMC (Heidelberg Multi Color) anomaloscope

3. Neitz anomaloscope

4. Pickford-Nicolson anomaloscope

Nagel’s anomaloscope:

GOLD STANDARD

Extraordinarily sensitive.

In this test the observer is asked to mixed red and green colors in such a proportion that the mixture should match the yellow colour disc.

Indication of defect is relative amount of red and green required.

Lantern test :

The test is performed in a dark room at 6 meters distance

It has five rotating discs

Disc 1 – aperture sizes varies 1.3 to 13 mm.

Disc 2-4 – Eight color filters (2 red, 2 green, white, yellow, blue,

Purple)

Disc 5 – a clear aperture, 5 neutral density filters, a ribbed glass

(simulate rain), frosted glass (simulate mist)

Recommendations of the test state that a candidate should be

rejected if he calls:

Red as Green

Green as Red

White light as Green or Red or vice versa

Red-Green or White light as black

Management and treatment :

Ideally there is NO treatment for the color blindness .But can help a person by -

Color blind person can see properly using a special

version of Adobe Photoshop.

There are special Monitors for Color Blind people

There are smart phones with a software, when seen through their camera shows the actual colors the way a normal person would see

Red Green Color Blind people can not see 3D movies which use Red and Green filters but can see recent 3D movies which are devised to be seen with glasses using crossed Polaroid lenses

X-chrome lens is a monocular (non-dominant)contact lens which significantly enhance color perception,

colormax lenses are tinted prescription spectacle lenses intended as an optical aid for people with red-green color vision deficiency

Do not help wearer to perceive or appreciate color like normal person but merely add brightness/darkness differences to color.

Gene therapy : cutting edge research

It is experimental aiming to convert congenitally color blind to trichromats by introducing photopigment gene

As of 2014 there is no medical entity offering this treatment

No clinical trial available for volunteers.

THANK YOU