Achromatopsia

Achromatopsia is a rare inherited condition affecting about one in 30,000 to 40,000 people. It affects the cone photoreceptors which are the specialist light-sensing cells responsible for colour vision and vision in bright light.

Symptoms of the condition appear early in childhood and include:

• Partial or total colour blindness
• Reduced visual acuity (sharpness of vision)
• Sensitivity to bright light (photophobia)
• Shaking eyes (nystagmous)

Recently, researchers at Moorfields Eye Hospital and UCL Institute of Ophthalmology were able to show that achromatopsia is a ‘stable’ condition with progression over time being relatively slow and subtle. People with achromatopsia do not go completely blind from the condition.

There are six genes which have been associated with achromatopsia: CNGB3 and CNGA3, which account for around 75% of all cases, as well as GNAT2, PDE6C, PDE6H and ATF6.

At the moment, achromatopsia is untreatable but red-coloured lenses can be used to reduce sensitivity to bright light. A number of novel interventions are currently under investigation including gene therapy.

The aim of gene therapy for the eye is to restore aspects of vision by using a harmless virus to introduce a normal copy of a defective gene into the cells where it is needed to make it available for use, essentially ‘replacing and correcting’ the defect.