sight seen_ gene therapy restores vision in both eyes_ scientific american

SIGHT FOR SORE EYES: A second round ofgene therapy for blindness worked just as well asthe first.Image: Garretttaggs55, Wikimedia Commons

Gene therapy has markedly improved vision

in both eyes in three women who were born

virtually blind. The patients can now avoid

obstacles even in dim light, read large print

and recognize people's faces. The operation,

researchers predict, should work even better

in children and adolescents blinded by the

same condition.

The advance, reported in the February 8

issue of Science Translational Medicine,

extends earlier work by the same group.

Between 2008 and 2011, Jean Bennett of the

University of Pennsylvania's Mahoney

Institute of Neurological Sciences and her

colleagues used gene therapy to treat

blindness in 12 adults and children with

Leber's congenital amaurosis (LCA), a rare inherited eye disease that destroys vision

by killing photoreceptors—light-sensitive cells in the retina at the back of the eye.

Typically, afflicted children start life with poor vision, which worsens as more and

more photoreceptors die.

The treatment grew out of the understanding that people with the disorder become

blind because of genetic mutations in retinal cells. One mutated gene that causes the

disorder is named RPE65. An enzyme encoded by RPE65 helps break down a

derivative of vitamin A called retinol into a substance that photoreceptors need to

detect light and send signals to the brain. Mutant forms of RPE65 prevent the

production of this enzyme in a "nursery" layer of cells called the retinal pigment

epithelium, which is attached to the retina and nourishes photoreceptors by breaking

down retinol, among other cellular services.

In the initial study, retina specialist and Bennett's co-author Albert Maguire of Penn

Medicine injected a harmless virus carrying normal copies of RPE65 into an area of

the retinal pigment epithelium, which subsequently began producing the enzyme. In

each of the 12 patients, Maguire treated one eye—the one with worse vision. Six

patients improved so much they no longer met the criteria for legal blindness.

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Sight Seen: Gene Therapy Restores Vision in Both Eyes: Scientific Ame... http://www.scientificamerican.com/article.cfm?id=gene-therapy-blindness

1 of 3 2012/02/27 10:43 AM

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In the new study, Maguire injected the functional genes into the previously untreated

eye in three of the women from the first group. Bennett followed the patients for six

months after their surgeries. The women's vision in their previously untreated eye

improved as soon as two weeks after the operation: They could navigate an obstacle

course, even in dim light, avoiding objects that had tripped them up before, as well as

recognize people's faces and read large signs. Bennett showed that not only were the

women's eyes much more sensitive to light, their brains were much more responsive

to optical input as well. Functional magnetic imaging showed regions of their visual

cortices that had remained offline before gene therapy began to light up.

Surprisingly, Bennett reports, the second round of gene therapy further strengthened

the brain's response to the initially treated eye as well as the newly treated one. "That

wasn't something we had been expecting, but it makes sense because the two eyes act

in concert, and some aspects of vision rely on binocularity." In the new paper, the

authors suggest that neuroplasticity plays a role: It is possible that regions of the

visual cortex responding to the newly flowing channel of information from the second

eye bolster activity in areas of the visual cortex responding to the initially treated eye.

An institutional review board required that Bennett work with adults in the follow-up

study, but she thinks the therapy will work even better in younger patients who have

not lost as many photoreceptors. She says the results "really bode well" for restoring

meaningful vision to people with LCA and other forms of inherited blindness.

Post a Comment | Read Comments (6)

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6 Comments Add Comment

1. DennyGH07:15 PM 2/8/12

This is a very interesting area of research. I'm wondering if

work like this is being done for people afflicted with macular

degeneration?

Reply | Report Abuse | Link to this

2. alan6302in reply to DennyGH10:15 PM 2/8/12

I think there are vitamins for that


3. imvrf12:09 AM 2/9/12

I am curious whether this has any application for those with

retinopathy of prematurity.


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2 of 3 2012/02/27 10:43 AM

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4. TigerWild08:10 AM 2/9/12

I am curious if there is a vision or thought adjustment in

persons who have what would be condisdered normal vision.

For the sake of pure science, they should extend the trials into

persons NOT afflicted with the mutated RPE65 and report the

results. It would be truly awesome to find another method that

enhances vision past laser enhancement. Maybe it could

correct color blindness, etc!


5. santaidm09:20 AM 2/9/12

My own sister is afflicted by the cone and rod disease which is

similar to LCA. That too can be fixed using gene therapy. The

problem lies with identifying the exact gene that causes the

problem. In her case Dr Robert Koenekoop has narrowed

down the gene location to a very small area and he believes he

will identify the gene in a matter of a few weeks/months.

Once this is done the rest of the procedure is well established

and working well, so there is hope.

I certainly do not want to induce false hopes but I think that

macular degeration is also being looked at as well as a number

of other diseases.

And Vitamin A, Lutein and Omega 3 are also appropriate to

prevent further damage while awaiting treatment. I am not a

health professional and my post is only intended to inform

others that there are possibilities.


6. gmperkins04:14 PM 2/9/12

@DennyGH There is and is an article in a past SciAm on that

topic. If memory serves, a virus was altered and then injected

into muscle tissue. The virus would invade muscle cells and

start producing a protein that basically says 'grow more

muscle'.

@TigerWild The retina is like the film, to improve eyesight

we'd need a better lens, lens manipulation or our eye would

need to be able to better reshape itself. Laser surgery modifies

the cornea in ways that bend light to better fit ones eye shape.

Perhaps denser retina cells would provide more detail but that

would go well beyond gene therapy. Same goes for, say, a

larger & more flexible lens combined with bigger eyes.


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3 of 3 2012/02/27 10:43 AM

sight seen_ gene therapy restores vision in both eyes_ scientific american

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