A cataract is the clouding of the eye’s lens and accounts for over half of all cases of blindness worldwide. Though cataracts can be effectively treated with surgery, it’s costly and requires trained surgeons. This is a problem for developing countries with poor health systems. Drug treatments have the potential to be a game changer in providing cheap and accessible treatment, but there are many hurdles. A new study that used eye drops to shrink cataracts in dogs may have made an important step in overcoming them.
The vast majority of cataracts are age related, but some can develop the condition as a result of an injury or a genetic defect. Researchers became more interested in researching how this defect led to cataracts. Professor Kang Zhang, from the University of California San Diego, and his research team studied two families who had children born with cataracts, known as congenital cataracts.
They found that those with congenital cataracts had a mutation in the gene that produces a small molecule known as lanosterol. The healthy version of this molecule usually prevents cataract-causing proteins from clumping together. In the abnormal version of this molecule, however, cataract-causing proteins caused cloudiness in the eye’s lens.
Zhang and his research team went on to develop eye drops that contained lanosterol as a drug treatment for cataracts. To test whether the eye drops could reduce cataracts, researchers isolated lenses from rabbits that had cataracts and placed them in a lanosterol solution for six days. They found that this reduced cataract severity and increased lens clarity.
“We went on to test the effect of the eye drops in dogs with cataracts. We gave them eye drops twice a day for six weeks and found it had reduced the effect of cataract severity,” Zhang explains to IFLScience.
Eye drops dissolved cataracts in dogs. Image credit: Kang Zhang
The study, published in Nature, only lasted for a few months, so the cataracts are likely to have reoccurred after the drops stopped, Zhang says. He does, however, believe that the eye drops could play an important role in the prevention of cataracts in those showing early signs. The ultimate “goal” is to develop a cheap, effective drug that can be widely used in low-resource settings.
Dr Manuel Datiles, a senior investigator and attending ophthalmologist at the National Eye Institute in the National Institutes of Health, tells IFLScience that though eye drops have the potential to overcome a number of limitations of surgery, they won’t be able to replace it yet.
“You cannot compare the improvements shown in this study with surgery. With cataract surgery, you become 20 years old again; with this one the lens is cleared up, but your vision can still be murky,” he explains.
The study is quite important, Datiles says, as researchers have discovered that a gene in a certain clinical pathway related to cholesterol production caused cataracts. This is, however, only one of the many pathways that can be used to alleviate cataracts.
“There are other drops that do the same thing but use different pathways. This is why we need multifunctional anti-cataract agents that work together across multiple pathways to clear the lens,” Datiles says.
“There’s now scope to investigate how we can combine this drug with other ones to better improve treatment,” he adds.
According to Datiles, eye drops will become key in treating cataracts, as surgery will not be able to cope with the growing needs of the world’s aging population. There’s already a backlog in many developing countries as clinics cannot cope with the demand for surgeries and, as a result, many become blind, Datiles says.