08/11/2015
Researchers in the US have developed a new
drug that can be delivered directly into the eye
via an eye dropper to shrink down and dissolve
cataracts - the leading cause of blindness in
humans.
While the effects have yet to be tested on
humans, the team from the University of
California, San Diego hopes to replicate the
findings in clinical trials and offer an alternative
to the only treatment that’s currently available to
cataract patients - painful and often prohibitively
expensive surgery.
Affecting tens of millions of people worldwide,
cataracts cause the lens of the eye to become
progressively cloudy, and when left untreated,
can lead to total blindness. This occurs when the
structure of the crystallin proteins that make up
the lens in our eyes deteriorates, causing the
damaged or disorganised proteins to clump and
form a milky blue or brown layer. While cataracts
cannot spread from one eye to the other, they
can occur independently in both eyes.
Scientists aren’t entirely sure what causes
cataracts, but most cases are related to age,
with the US National Eye Institute reporting that
by the age of 80, more than half of all Americans
either have a cataract, or have had cataract
surgery. While unpleasant, the surgical
procedure to remove a cataract is very simple
and safe, but many communities in developing
countries and regional areas do not have access
to the money or facilities to perform it, which
means blindness is inevitable for the vast
majority of patients.
According to the Fred Hollows Foundation , an
estimated 32.4 million people around the world
today are blind, and 90 percent of them live in
developing countries. More than half of these
cases were caused by cataracts, which means
having an eye drop as an alternative to surgery
would make an incredible difference.
The new drug is based on a naturally-occurring
steroid called lanosterol. The idea to test the
effectiveness of lanosterol on cataracts came to
the researchers when they became aware of two
children in China who had inherited a congenital
form of cataract, which had never affected their
parents. The researchers discovered that these
siblings shared a mutation that stopped the
production of lanosterol, which their parents
lacked.
So if the parents were producing lanosterol and
didn’t get cataracts, but their children weren’t
producing lanosterol and did get cataracts, the
researchers proposed that the steroid might halt
the defective crystallin proteins from clumping
together and forming cataracts in the non-
congenital form of the disease.
They tested their lanosterol-based eye drops in
three types of experiments. They worked with
human lens in the lab and saw a decrease in
cataract size. They then tested the effects on
rabbits, and according to Hanae Armitage at
Science Mag, after six days, all but two of their
13 patients had gone from having severe
cataracts to mild cataracts or no cataracts at all.
Finally, they tested the eye drops on dogs with
naturally occurring cataracts. Just like the
human lens in the lab and the rabbits, the dogs
responded positively to the drug, with severe
cataracts shrinking away to nothing, or almost
nothing.
The results have been published in Nature.
"This is a really comprehensive and compelling
paper - the strongest I’ve seen of its kind in a
decade," molecular biologist Jonathan King from
the Massachusetts Institute of Technology (MIT)
told Armitage . While not affiliated with this study,
King has been involved in cataract research for
the past 15 years. "They discovered the
phenomena and then followed with all of the
experiments that you should do - that’s as
biologically relevant as you can get."
The next step is for the researchers to figure out
exactly how the lanosterol-based eye drops are
eliciting this response from the cataract proteins,
and to progress their research to human trials.
