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Achromatopsia – causes, symptoms and treatment
Medically reviewed by Sharon Copeland on 23rd June 2022
Achromatopsia (ACHM) is a rare inherited eye condition where a person lacks colour vision because of disorder of the retina, meaning, the person is not able to see any colours. Other names of this condition are Achromatism, Day blindness Rod monochromatism and Total colour blindness. This condition can be partial or complete. People with complete achromatopsia cannot see any other colours except for black, white and shades of grey, while a partial achromatopsic person is able to perceive some colours.
What causes achromatopsia?
Achromatopia is caused by a disorder of the retina, which is the light-sensitive tissue at the back of the eye. The retina has two types of photoreceptor cells – rods and cones.
Rod cells - these cells are responsible for providing vision in low light or during the night.
Cone cells – these photoreceptor cells in the retina are responsible for colour vision and eye colour sensitivity.
These cells transmit the signal from the eyes to the brain helping us to see things. Absence of cone cells causes achromatopsia.
This disorder is passed on to a child by their parents and is a result of changes in one of the following genes - CNGA3, CNGB3, GNAT2, PDE6C, or PDE6H; CNGB3 and CNGA3 being the most common mutated genes.
Mutations in these genes prevent cones from reacting with light, therefore preventing us from seeing colours. This condition is inherited in an autosomal recessive manner, meaning, both the parents have passed on a mutation in a gene causing achromatopsia in their child. Usually, the parents do not show any symptoms but are the carriers of the genes.
Cones are completely non-functional in the case of people with complete achromatopsia, hence they cannot see any colours. People with partial/incomplete achromatopsia retain some cone cells and have limited colour vision.
What are the symptoms of achromatopsia?
Children suffering from achromatopsia have poor vision from birth or early infancy.
Look out for the following signs in your child:
- Discomfort in bright conditions (photophobia)
- Reduced or blurred vision/ difficulty in seeing while playing games or reading
- Limited or absent colour vision, such as, your child might not be able to identify colours
- Involuntary rhythmic eye movement: this could be side to side, circular or up and down (nystagmus) movement of eyeballs
According to Ophthalmology Times, people with this disorder will have poor central vision in the range of 20/100 to 20/200; they will have difficulty in reading, seeing pictures or faces and, identifying colours, shapes etc.
The severity of the symptoms will also depend on the type of achromatopsia your child is suffering from – complete or partial. Partial achromatopsia will show less critical signs.
What are the effects of achromatopsia?
People diagnosed with this disorder are at risk of developing other vision problems such as:
- Photophobia or increased sensitivity to light, such as being sensitive to indoor/outdoor light lamps or the sun, and they wouldn’t want to go out during the day
- Near-sightedness or myopia; having difficulty in reading small prints such as a newspaper or a book
- Far-sightedness or hyperopia; finding it difficult to see a far away object such as a road sign
How is achromatopsia diagnosed?
First your ophthalmologist will discuss any history of vision disorder with you. The diagnosis is then carried out with an ERG (electroretinogram). An ERG reveals the inactivity/ absence of cone receptors in the retina through a retinal examination and genetic testing.
Genetic Testing is available to assess the risk of passing this disease from parents to their child.
The number of tests will depend on the age of the child, an infant might go through basic tests, whereas an older person/child might have to go through more tests.
Can achromatopsia be cured?
Presently, there is no cure for this disorder. However, several clinical trials, such as Retina UK are engaging in research to find a cure for this disorder.
An emerging therapy known as gene therapy could help to improve the quality and sight of the people suffering with achromatopsia.
Visual aid for achtomatopsia
- Lenses - to help ease this disorder red-coloured or dark-tinted lenses can be used to reduce sensitivity to bright light
- Glasses - people with achromatopsia also wear glasses with tinted lenses to deflect the light to make them less uncomfortable during the daytime
Is achromatopsia the same as colour blindness?
Achromatopsia is not the same as colour blindness.
A colour-blind person has difficulty distinguishing between colours such as green and red. An achromatopsic person can only perceive black, white and shades of grey.
How common is achromatopsia?
This condition is a rare hereditary vision disorder. One in 30,000 to 40,000 people worldwide are affected by achromatopsia. Complete achromatopsia is more common than the other form.
Can people suffering with achromatopsia go blind?
This disorder is a ‘stable’ condition which increases moderately as the child grows older, however this growth is slow and subtle. According to the researchers at Moorfields, NHS, people suffering with this disorder do not go completely blind.