By HELEN BRIGGS - BBC NEWS - HEALTH
Added: Thu, 09 Feb 2012 13:13:52 UTC
Three US citizens who lost their sight in childhood have reported a dramatic improvement in vision after having gene therapy in both eyes.
There was some improvement after the genetic fault in one eye was corrected four years ago.
Now, one woman has described her joy at seeing her children's faces, after her second eye was treated.
Tami Morehouse: 'It's just incredible to see'
The research increases hopes that gene therapy can be used in a range of eye conditions, said a UK expert.
The three have Leber's Congenital Amaurosis (LCA), a rare inherited disease caused by defects in a gene encoding a protein needed for vision.
It appears at birth or in the first months of life, leading to severely impaired vision, involuntary eye movements and poor night vision.
The disorder, which can be caused by 'mistakes' in more than 10 different genes, prevents normal function of the retina; the light-sensitive layer of cells at the back of the eye.
Several teams around the world are carrying out early trials of gene therapy in blindness, including experts at the Philadelphia Children's Hospital and the University of Philadelphia, US.
Only a handful of patients worldwide have received the treatment to boost a faulty gene underlying an inherited form of blindness.