The French RP Association also funded this project. LCA is thought to account for five per cent of all inherited retinal degenerative diseases. LCA1 is thought to be the most common form of the disease. Mutations in this gene are thought to interfere with the visual transduction cascade by which photoreceptors convert light into an electrical signal which is sent to the brain to produce sight. Of all retinal degenerative diseases, LCA has the earliest onset.
Patients have severe visual impairment at birth.
Visual acuity is usually limited to counting fingers or detecting hand motions or bright lights. Many children with LCA habitually press on their eyes with their fists or fingers. This habitual pressing on the eyes is known clinically as the oculo-digital sign. Some patients with LCA also experience brain or developmental abnormalities.