Leber's congenital amaurosis (LCA) is an
inherited degenerative disorder affecting the retina, a light sensitive tissue
at the back of the eye which detects light and color. People who suffer from
this disease usually have severe visual impairment right from childhood, may be
even starting at infancy. Children affected with LCA usually lack night vision
and some may even lose daylight vision.
The clinical manifestations include reduced electroretinograms and pupillary
light reflexes, nystagmus (rhythmic, involuntary eye fixation instability) as
well as fundus abnormalities on ophthalmoscopy.
It is estimated that about 10% of patients affected
with LCA have a mutated
form of the gene retinal
pigment epithelium-specific 65 kDa (RPE65), which is a protein critical
for vision. The RPE65 protein produces a specific form
of vitamin A that enables the light-sensitive photoreceptor cells to function.
Mutations in the RPE65 gene thus halts the visual cycle and blocks vision.
RPE65 gene replacement therapy
was considered as a
therapeutic strategy in patients with LCA. A study was conducted on 15 people
suffering from LCA, who received a retinal injection of a virus that was
designed to produce healthy RPE65. The results of the
study were published in the New
England Journal of Medicine
After few days of treatment, some patients
demonstrated a remarkable increase in their ability to see dim light, which
they had never seen before.
G. Jacobson, the lead scientist from the University of Pennsylvania's Scheie
Eye Institute, Philadelphia, commented, "Gene therapy for LCA
demonstrated, we could improve vision in previously untreatable and incurable
out of the fifteen patients reportedly started relying on the area of the retina
where the gene therapy injection was given to see lettershus extending their
These results are quite significant because they
represent one of the important steps towards the clinical use of gene therapy
for an inherited form of blindness.
further added, "We've been able to positively alter and extend the visual
life of patients with LCA, and we now have to develop workable strategies for
extending it even further."
study findings suggest that it may be possible to achieve substantial restoration of vision
patients with LCA as long as gene replacement was performed at an early stage
in the disease.