Therapeutic eye injections may be needed less often

August 19, 2013
Therapeutic eye injections may be needed less often
This is a diagram of a healthy human eye. The macula is marked at the back of the eye with a black oval. Credit: National Eye Institute, National Institutes of Health

Johns Hopkins biomedical engineers have teamed up with clinicians to create a new drug-delivery strategy for a type of central vision loss caused by blood vessel growth at the back of the eye, where such growth should not occur. In addition to testing a new drug that effectively stops such runaway vessel growth in mice, the team gave the drug a biodegradable coating to keep it in the eye longer. If proven effective in humans, the engineers say, it could mean only two or three needle sticks to the eye per year instead of the monthly injections that are the current standard of care.

The new , in its time-release coating, was tested in with abnormalities similar to those experienced by people with neovascular age-related , or "wet" AMD. A description of the study results, currently available online, will be published in the October issue of the journal Biomaterials.

"If you lose central vision, you can't drive a car and you can't see your ," says Jordan Green, Ph.D., assistant professor of biomedical engineering and at The Johns Hopkins University. "You're willing to do what it takes to keep your sight. We hope that our system will work in people, and make invasive treatments much less frequent, and therefore easier to comply with, and safer."

According to Peter Campochiaro, M.D., the George S. & Dolores Doré Eccles Professor of Ophthalmology & Neuroscience, approximately 200,000 Americans suffer from central vision loss caused by wet AMD. The macula is a few square centimeters of tissue in the center of the retina at the back of the eye. It is responsible for the majority of a person's high-resolution vision, especially the high-res vision needed for driving and reading. There are normally no in the outer part of the retina because it needs to be unobstructed to capture complete images. In patients with wet AMD, blood vessels from behind the retina can break through into the macula and leak fluid that reduces vision. This initially causes reversible loss of vision, but, if left untreated, visual loss becomes permanent.

Therapeutic eye injections may be needed less often
This is a diagram of a microparticle that slowly releases a drug for treating "wet" age-related macular degeneration. The drug (blue) is encapsulated in hundreds of nanoparticles (green), which are then encapsulated in a microparticle (brown). Credit: Jordan Green

Currently, wet AMD patients are treated with frequent (as often as once a month) injections into the eye of a drug that blocks one of the major stimulators of abnormal . "Patients are given localized antibacterial and pain-numbing agents, and then a very fine needle is passed through the white of the eye into the central cavity where the drug is injected. It's not painful, but it isn't something that patients enjoy," says Campochiaro. "The frequent visits for injections are a burden and each injection carries a small risk of infection, so one of our goals is to find new approaches that allow for fewer visits and injections."

Green's laboratory, which specializes in designing new drug-delivery systems, worked with Campochiaro and Aleksander Popel, Ph.D., professor of , whose laboratory discovered the new drug—a short piece of protein that blocks the growth of unwanted blood vessels. (The drugs currently on the market for treating wet AMD are longer protein pieces or full-length proteins that could become inactive if given a biodegradable coating.)

When the team tested the drug on cells grown in the lab, they found that it killed blood vessel cells and prevented growth of new blood vessels. The same effect was found when the drug was injected into the eyes of mice with abnormal blood vessels like those seen in wet AMD, but, as with the current standard treatment, the drug was only effective for about four weeks since the watery contents inside the eye gradually flushed it out.

The team's solution, says Green, was to slow the release and depletion of the drug by covering it in non-toxic, biodegradable coatings. They first created "nanoparticles," tiny little spheres filled with the drug. When the spheres were placed in a watery environment, the water gradually broke down the coating and released the drug a little at a time. To maximize this effect, the team created larger spheres, called microparticles, filled with about a hundred nanoparticles per microparticle, and held together by another type of biodegradable "glue." The end result is something like a scoop of gumball ice cream. As the ice cream gets licked away, more and more gumballs (nanoparticles) are exposed.

Testing their microparticles in mice, the team found that the drug persisted in their eyes for at least 14 weeks, more than three times as long as the current treatment. Green says that the treatments may last longer in humans than in mice, but clinical trials will not begin before further testing in other animals.

Explore further: New drug could help AMD sufferers

More information: dx.doi.org/10.1016/j.biomaterials.2013.06.044

Related Stories

New drug could help AMD sufferers

June 18, 2013

There is no cure for age-related macular degeneration, an eye disease that is the leading cause of vision loss and blindness in older Americans. Last year, the National Institutes of Health reported that two drugs injected ...

Device designed to treat a leading cause of blindness

February 29, 2012

(Medical Xpress) -- Every year, more than 200,000 people in the U.S. are diagnosed with Wet Age-Related Macular Degeneration, a leading cause of blindness in Americans age 60 or older. There is no known cure for the disease, ...

Recommended for you

A pocket-sized retina camera, no dilating required

March 20, 2017

It's the part of the eye exam everyone hates: the pupil-dilating eye drops. The drops work by opening the pupil and preventing the iris from constricting in response to light and are often used for routine examination and ...

Scientists deploy CRISPR to preserve photoreceptors in mice

March 14, 2017

Silencing a gene called Nrl in mice prevents the loss of cells from degenerative diseases of the retina, according to a new study. The findings could lead to novel therapies for preventing vision loss from human diseases ...

New help for that bane of middle-age: blurry close-up vision

February 28, 2017

Squinting while texting? Always losing your reading glasses? An eye implant that takes about 10 minutes to put in place is the newest in a list of surgical repairs for the blurry close-up vision that is a bane of middle age. ...

Vitamin B3 prevents glaucoma in laboratory mice

February 16, 2017

In mice genetically predisposed to glaucoma, vitamin B3 added to drinking water is effective at preventing the disease, a research team led by Jackson Laboratory Professor and Howard Hughes Medical Investigator Simon W.M. ...

GARP2 accelerates retinal degeneration in a mouse model

February 15, 2017

In the retina of the eye, rod and cone cells turn light into electrical signals, the first step toward human vision. University of Alabama at Birmingham researchers are studying rod cell proteins GARP1 and GARP2 to learn ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.