D i.e. Blue & yellow 
Macular lesion tends to produce blue-yellow defects and optic nerve lesions produce red green defects 

B i.e. Hereditary Colour Blindness (Achromatopsia)

• An individual with normal colour vision is k/a trichromate. In colour blindness, the ability to appreciate one or more primary colours is either defective (anomalous) or absent (anopia). It may be congenital or acquired.
• Colour blindness is usually a hereditary condition that is present by birth, and though it is more common in males, it can occur in females also. It can also be an acquired condition through diseases of optic nerve or macula but is not normal age-related phenomena. There is no treatment.
• Red & green pigment cones are coded on X-Chromosome and Blue cones on Chromosome 7.

A i.e. More common in males
Color blindness occurs when you are unable to see colors in a normal way. It is also known as color deficiency. 
Men are at much higher risk for being born with color blindness than women
Most people with color blindness are born with it. This is called a congenital condition. Congenital color vision defects usually pass from mother to son.

D. i.e. Tritanomalous

• So anopics have dichromatic colour vision i.e. (are able to see two primary colours) & anomalous have trichromatic colour vision with anomaly (i.e. mechanism to appreciate all 3 primary colours is present but is defective for one or two of them)
• Protan means first, deutan means second, and tritan means third. According to decreasing wavelength it is used for red (550-570 nm, so protan), green (520-540 nm, so deuteran) and blue (410-424 nm, so tritan).

A i.e. Red
people affected by protan color blindness are less sensitive to red light, deuteranopia or deuteranomly (the second type of red-green color blindness) is related to sensitiveness on green light.

C i.e. Protanomaly
Protans are people with protanomaly, a type of red-green color blindness in which the red cones do not detect enough red and are too sensitive to greens, yellows, and oranges.

A i.e., Mainly congenital B i.e., Can be tested by Farnsworth 100 hue test; C i.e. Ishihara chart test red/ green colour blindness 

Tests for color vision

Pseudoisochromatic charts

–   Ishihara plates mainly to screen congenital protan & deuterans (i.e., red & green defects)

–   Hardy -Rand – Rittler plates is more sensitive to Ishihara since it can defect all three congenital defects

Edridge Green lantern test : the subject has to identify various colours shown to him (in lantern) & judgment depends on mistake he makes.
City university test : a spectroscopic test where subject is asked to match central colour to its closest hue from 4 peripheral surrounding colour in each of 10 plates.
Fansworth Munsell 100 hue test is the most sensitive for both congenital & acquired color defects. It consists of 85 hue caps (not 100) and vision is judged by error score i.e., higher score = poorer vision.
Fansworth D 15 hue discrimination test is similar test but utilizes only 15 hue caps
Nagel’s anomaloscope (asked to mix red & green to make a given shade)
Holmgren’s wool test

Ans. Sex-linked disorder
Colour blindness is a usually a genetic (hereditary) condition (you are born with it). Red/green and blue colour blindness is usually passed down from your parents. The gene which is responsible for the condition is carried on the X chromosome 

Ans. Increased sclerosis of the crystalline lens

• Acquired blue colour defect (blue blindness) may occur in old age due to increased sclerosis of crystalline lens. 
• As perceived by the human eye; light consists of those wavelengths of electromagnetic radiation (approximately 400-700nm).
• Normal colour vision is known as trichromate.
• Normal human eye can appreciate three primary colours (red, green & blue) due to presence of 3 different type of cones.

Ans.B. Deuteranopes
Red-green color blindness is the most common type of color deficiency. Also known as deuteranopia, this is most likely a congenital condition.

For defective (anomalous) colour vision, suffix anomalous is used; and for absent colour suffix anopia is used.