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Leber Congenital Amaurosis
Leber congenital amaurosis (LCA) is a rare and inherited retinal degeneration (IRD) which is characterised by severe visual impairment at birth or within the first few months of life.
LCA occurs due to improper function and degeneration of the rod and cone photoreceptor cells in the retina. These light-sensitive photoreceptor cells fail to correctly transmit electrical signals, resulting in visual impairment. Due to the severity of the condition, research into developing therapies for LCA has been extensive and there have been numerous clinical trials for the condition, with many more ongoing.
What are the symptoms of LCA?
LCA is commonly detected in children who display profound visual impairment, don’t show clear focus on anything within their environment and it is characteristic for children to rub and press their eyes, a behaviour which is called Franceschetti’s oculo-digital sign. This can cause damage to the cornea (keratoconus) and lens and may result in a loss of fatty tissue around the eyes causing the eyes to look deep-set.
Involuntary eye movements (nystagmus), increased light-sensitivity (photophobia) and far sightedness (hyperopia) are other symptoms associated with LCA. The extent of degeneration depends on the type of LCA the child has and for some types of LCA the vision (or lack of vision) remains stable.
What Causes LCA?
LCA is a rare genetic condition affecting 2 to 3 people per 100,000 newborn children and arises due to a mutation in one of a wide variety of genes; CEP290, RPE65, GUCY2D, RPGRIP1, RDH12, SPATA7, AIPL1, RD3, CRB1, CRX, IMPDH1, IQCB1, KCNJ13, LCA5, NMNAT1, and TULP11. Some of these genes are necessary for the normal development of the rod and cone photoreceptor cells, phototransduction and cilia formation, the latter of which is very important for perceiving many forms of sensory input, including vision and hearing1.
LCA most frequently has an autosomal recessive pattern of inheritance, meaning that two faulty gene copies are required for LCA to develop. However, some gene mutations have an autosomal dominant pattern of inheritance, causing LCA to occur when only one faulty gene copy is present.
More information on genetic inheritance can be found in our Genetics and Inheritance section.
Electroretinograms are frequently used to examine the activity levels of the retina and evaluates the rod and cone photoreceptor cells. People living with LCA generally have very limited retina function and can be diagnosed in this way. Additionally, genetic testing to identify mutations in any of the associated genes also ensures the correct condition is diagnosed.
What treatments are available?
Luxturna (voretigene neparvovec-rzyl) is the first gene-therapy approved for treating certain forms of LCA, specifically LCA caused by mutations in both RPE65 gene copies. This revolutionary gene-therapy works by replacing the two faulty copies with normal functioning RPE65 gene copies into the cells at the back of the retina to restore normal vision. Luxturna is administered as a one-time sub-retinal injection.
To date, there are no other approved treatments for LCA, but there is an extensive amount of time being invested in clinical research to develop more treatments. Make sure to to keep up to date with recent progress in research and clinical trials by visiting the clinicaltrials.gov website.
It is also very important that people with the LCA continue to have regular eye exams as they may develop other retinal conditions, some of which can be treated.
References
1. National Institute of Health. Available at https://ghr.nlm.nih.gov/condition/leber-congenital-amaurosis#inheritance. Accessed April 2020.