Colour blindness
Colour blindness is not a form of blindness at all, but a deficiency in the way you see colour. If you are colourblind, you have difficulty distinguishing certain colours, such as blue and yellow or red and green.
Colour blindness is an inherited condition that affects males more frequently than females.
Red-green colour deficiency is the most common form of colour blindness.
Sign and symptoms –
Most people who are considered colorblind can see colours, but certain colours appear washed out and are easily confused with other colours, depending on the type of colour vision deficiency they have.
If you develop colour vision problems when normally you have been able to see a full range of colour, then you definitely should visit your optician.
Sudden or gradual loss of colour vision can indicate any number of underlying health problems, such as cataracts.
Types –
Our eyes contain photoreceptors called rods and cones. Rods are the cells that sense light and dark. Cone cells are sensitive to the different wavelength of light and are responsible for color perception. They are divided into three types –
• Red light (Long wavelength)
• Green light (Medium wavelength)
• Blue light (Short wavelength)
A person with normal color vision has trichromacy which means you have a normal amount of all three comes types. Someone with a colour vision deficiency may lack all or some cones –
• Dichromacy means you only have two types of functioning cones.
• Anomalous trichromacy means all three types of cones are present, but one of the cone types does not detect color normally.
• Monochromacy or achromatopsia occurs when only one or none of the cones function normally.
The most common form of colour blindness is red-green. Most people with this deficiency inherit it as a recessive X-chromosome linked trait,which means a mother who is colour blind or who is a carrier can pass this condition to her child.
There are different types of red-green blindness –
• Deuton Types
This type have a deficiency in green cones. Deuteranopia means a complete lack of green cones (Dichromacy).Deuteranomaly means a shift in the color sensitivity of the green cones.
• Protan Types
This type have a deficiency in red cones. Protanopia means a complete lack of red cones. Protanomaly means a shift in the color sensitivity of the red cones.
Those with red-green colour deficiencies tend to confuse purple and blue as well as green, orange and red.
The blue-yellow type of colour is rare.The types of blue-yellow colour blindness are –
• Tritan types
This type have a deficiency in blue cones. Tritanopia means a complete lack of blue cones.Tritanomaly means a shift in the color sensitivity of the blue cones.
Tritan types tend to confuse blue and green, as well as orange, yellow and red.
Causes –
Colour blindness occurs when light sensitive cells in the retina fail to respond appropriately to variations in wavelengths of light that enable people to see an array of colours.
Photoreceptors in the retina are called rods and cones. Rods are more plentiful and they are more sensitive to light than cones, but rods are incapable of perceiving color. The photoreceptors are concentrated in the central zone of the retina called the macula.
The center of the macula is called the fovea, and this tiny area contains the highest concentration of cones in the retina and is responsible for our most acute colour vision.
Besides differences in genetic makeup, other causes of colour vision defects or loss include –
• Parkinson’s disease (PD)
• Cataracts
• Certain medications e.g. anti-seizure drugs
• Kallman’s syndrome
• Leber’s hereditary optic neuropathy (LHON)
Colour vision Testing –
The most common type of colour vision test opthalmologists use is the Ishihara test. The test plates contain dots in various colours.Typically, there is a number on each test plate.
Your doctor will ask you to identify what you see on each page. Those with colour deficiencies may not be able to see any number or pattern on a given page.
Another test that uses colour plates in the Hardy, Rand and Rittler (HRR) test. The test looks very similar to the ishihara test. However, the most significant difference is that the ishihara test only screens for red-green deficiencies while the HRR test can also screen for blue-yellow colour vision problems.
Both of these tests are only screening tools and donot pick up or subtle colour vision deficiencies. If your doctor suspects a colour vision problem, they may administer more sophisticated colour vision testing, called arrangement tests.
The Farnsworth-Munsell 100-hue test provides more detailed information than colour plates test. Farnsworth D-15 test is a shortened version of this test. Both of these lists require the patient to arrange several coloured discs in a particular corder.
Treatment –
There are no treatments for most types of colour vision difficulties, unless the colour vision problem is related to the use of certain medicines or eye conditions. Discontinuing the medication causing your vision problem or treating the underlying eye disease may result in better color vision.
Wearing a coloured filter over eyeglasses or a coloured contact lens may enhance your perception of contrast between the confused colours. But such lenses won’t improve your ability to see all colours.
Ayurvedic Treatment –
• In Ayurveda Panchakarma, treatments likeTarpana, has been advocated highly beneficial for the treatment of colour blindness. Taking Triphala Ghritham, an ayurvedic medication for Tarpana is considered to be very beneficial in the treatment of colour blindness.
• Some herbal medicines like Saptamrit Lauh and Amrit Rasayan are very good for providing nutritional benefits to eyes.
• Amla juice is the best alternative for improving the eyesight.
• A balanced diet and green leafy vegetables are very useful.
Though any specific treatment of colour blindness is still in vague, ayurvedic treatment of colour blindness can help to reduce the effects
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