More than 20 million Americans have cataracts, a leading cause of vision loss and blindness, and right now surgery is the only available option to correct the problem. But new research raises the hope that someday, cataracts could be cured with simple eye drops.
Cataracts occur when the normally transparent lens of the eye gradually clouds over due to an accumulation of proteins that malform and clump together. The condition often develops as people get older; the National Eye Institute estimates that by the age of 80, more than half of all Americans either have a cataract or have had surgery to remove one.
Now researchers from the University of California, San Diego have discovered a promising alternative to surgery: an eye drop that effectively reversed cataracts in animal testing. Their findings are published in the journal Nature.
Their work began with the cases of three children who had a severe cataract condition that ran in their family. The scientists sequenced the children's genomes and identified a genetic mutation that interfered with the production of lanosterol, a naturally occurring steroid in the body. From that clue, they decided to test whether lanosterol might have the ability to prevent or even eliminate cataracts.
They tested it first in lab cultures, then in the cataract lenses of rabbits, and finally on 7 dogs from 3 species (black Labrador, Queensland Heeler and Miniature Pinscher ) who were suffering from adult-onset cataracts, which can happen in canines as well as humans.
For the dogs' treatment, they sedated the animals and injected lanosterol (100 mg)-loaded nanoparticles into the vitreous cavity of the eye, the area behind the lens which is filled with a gel-like substance called the vitreous humor. The treatment eyes then received lanosterol in topical eye drops, one drop three times a day for 6 weeks.
"Treatment by lanosterol," the researchers write, "significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments."
The dogs who received the treatment showed notable improvement in their cataracts, graded on a scale from zero (no cataract) to 3 (extensive opacity of the entire lens).
"I was pleasantly surprised, even in principle, this treatment should work," one of the authors of the study, Dr. Kang Zhang, professor of ophthalmology and chief of ophthalmic genetics at UC San Diego, told CBS News.
Other scientists in the field were impressed by the results.
In a commentary published in Nature to accompany the study, J. Fielding Hejtmancik, of the Ophthalmic Genetics and Visual Function Branch of the National Eye Institute, suggested the research could lead to non-surgical prevention and treatment of cataracts.
"The potential for this finding to be translated into the first practical pharmacological prevention, or even treatment, of human cataracts could not come at a more opportune time," he writes.
"This is a really comprehensive and compelling paper - the strongest I've seen of its kind in a decade," Jonathan King, a molecular biologist at Massachusetts Institute of Technology who researches cataract proteins, told Science magazine. "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."
Before testing can begin in humans, Zhang said the team will need to check the toxicity of lanosterol, even though it is "a product of our own body. Then we will need to formulate the drug as the most efficient eye drop for a human trial."
In a Nature podcast, Zhang said he and his colleagues hope to begin human trials within a year.