welcome to disease section for color blindness 

Photoreceptor cells
Photoreceptor cells

A photoreceptor cell found in retina is a specialized type of neuron that converts light into electrical signals that can stimulate biological processes. These signals are transmitted to the brain through the optic nerve. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system. Damage to photoreceptors in retina often leads to color blindness. Color blindness can be mild or severe. Damage can be due to heridity, eye injury, effects of other diseases on eye, etc. Based on photopigment defects in cones (responsible for colors),  there are three main kinds of color blindness. Red-green color blindness is the most common, followed by blue-yellow color blindness.

Structure of eye retina
Structure of eye retina

The retina is a light-sensitive layer in the inner surface of the eye. It surrounds the vitreous body and extends outwards with the optic nerve. In the retina, the first layer is pigment epithelium which extends over the optic section of the retina and borders directly on the underlying choroid. The second layer is made up of ten layers i.e. inner limiting membrane, stratum opticum, the ganglion cell layer, the inner plexiform layer, the inner nuclear layer, the outer plexiform layer, the outer nuclear layer, the external limiting membrane and the layer of rods and cones. Rods are sensitive in dim light and cones are sensitive in bright light. Colorblindness is a disorder in which light-sensitive cells or photoreceptor cells in the retina fail to respond appropriately to variations in wavelengths of light for color vision.

Retinal cells and color pereption
Retinal cells and color pereption

Color perception helps the humans (and many other animals) to differentiate objects on the basis of the distribution of the wavelengths of light that they reflect to the eye. When light enters the eye, retinal cells are responsible for color distinction. Rods are responsible for night vision and cones are responsible for color and bright light vision. Cone photoreceptors convert a light signal into an electrical signal. These cells are converted into opponent colors in retinal ganglion cells and are interpreted in visual cortex.

Human vision and color differentiation
Human vision and color differentiation

Human visual perception system is crucial ad complex. It depends on the eye and brain to how to distinguish color depending upon the intensity of light entering the eye. The retina in the eye contains cell called rods and cones which are sensitive to different colors of light. Depending upon the wavelength of light, different colors can be differentiated. When light enter the eye, it sends signals to the brain. The light sensitive cells define the wavelength to the brain and the visual area of thalamus distinguishes the color.

Color perception
Color perception

Color perception depends on the absorption of light by three different spectral classes of cones. It also depends on the brain’s response to the stimuli that are produced when light reacts with the retinal cells in the eye. When light-sensitive cells in the retina fail to respond appropriately to different light wavelengths, it causes color blindness. Color blindness is a kind of deficiency to see colors. It is more accurately known as color vision deficiency. It is an inherited condition and is more found in males. With this vision problem, it is difficult to distinguish among certain colors, such as blue and yellow or red and green.

Eye Anatomy
Eye Anatomy

The eye is our organ of sight. The eye has a number of components which include but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve, choroid and vitreous. The retina of the eye has two types of light-sensitive cells - rods and cones. Cones are responsible for colour discrimination. The exact cause of colour blindness is still to be found but it is believed that colour blindness is usually caused by faulty cones. If you have inherited colour blindness, your condition will stay the same throughout your life. It won't get any worse or better over time.

Different types of color blindness
Different types of color blindness

There are three main types of color blindness (color vision deficiency), based on photopigment defects in the three different kinds of cones that respond to blue, green, and red light. Red-green color blindness is the most common, followed by blue-yellow color blindness. A complete absence of color vision called total color blindness is rare.

 In males with deuteranopia, there are no working green cone cells. In males with protanopia, there are no working red cone cells. People with tritanopia, also known as blue-yellow color blindness, lack blue cone cells.

Different types of color blindness and color perception
Different types of color blindness and color perception

 In males with deuteranopia, there are no working green cone cells. In males with protanopia, there are no working red cone cells. People with tritanopia, also known as blue-yellow color blindness, lack blue cone cells. People with tritanomaly have limited blue cone cells. In males with protanomaly, the red cone photopigment is abnormal. In males with deuteranomaly, the green cone photopigment is abnormal.