Eye infection in contact lens wearers due to poor hygiene can cause blindness

Posted on March 31, 2019 by Dawn Kaplan

There are reports of an outbreak of a rare but essentially preventable eye infection that can cause blindness, identified in contact lens wearers in a new study led by UCL and Moorfields Eye Hospital researchers. The research team found a threefold increase in Acanthamoeba keratitis since 2011 in South-East England.

The findings showed that reusable contact lens wearers with the eye infection were more likely to have used an ineffective contact lens solution, have contaminated their lenses with water or reported poor contact lens hygiene. “This infection is still quite rare, usually affecting 2.5 in 100,000 contact lens users per year in South East England, but it’s largely preventable. This increase in cases highlights the need for contact lens users to be aware of the risks,” said the study’s lead author, Professor John Dart (UCL Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust).

Acanthamoeba keratitis is an eye disease that causes the front surface of the eye, the cornea, to become painful and inflamed, due to infection by Acanthamoeba, a cyst-forming microorganism.

The most severely affected patients (a quarter of the total) have less than 25% of vision or become blind following the disease and face prolonged treatment. Overall 25% of people affected require corneal transplants to treat the disease or restore vision.

Anyone can be infected, but research shows that contact lens users face the highest risk, due to a combination of increased exposure to infection, for reasons not fully established, as a result of contact lens wear and contamination of lens cases.

Alongside these findings, they conducted a case-control study of people who wear reusable contact lenses on a daily basis (although the disease is also associated with disposable lenses), comparing those who had a diagnosis of Acanthamoeba keratitis to those who had come in to Moorfields A&E for any other reason, from 2011 to 2014.

The case-control study included 63 people with Acanthamoeba keratitis and 213 without. They all completed a questionnaire, from which the researchers found that the risk of developing the disease was more than three times greater amongst people with poor contact lens hygiene, people who did not always wash and dry their hands before handling their lenses, those who used a lens disinfectant product containing Oxipol (now phased out by the manufacturer), and for people who wore their contacts while in swimming pools or hot tubs. Showering and face washing while wearing contact lenses are also likely to be risk factors.

Acanthamoeba is more commonly found in the UK than in other countries, likely due to higher levels found in domestic (as opposed to mains) water supplies, so that water contamination of contact lenses is of particular concern in the UK.

The researchers say the current outbreak is unlikely to be due to any one of the identified risk factors in isolation.

“People who wear reusable contact lenses need to make sure they thoroughly wash and dry their hands before handling contact lenses, and avoid wearing them while swimming, face washing or bathing. Daily disposable lenses, which eliminate the need for contact lens cases or solutions, may be safer and we are currently analysing our data to establish the risk factors for these,” said Professor Dart.

To read to original article in its entirety, click here. https://www.sciencedaily.com/releases/2018/09/180921082952.htm

Human retinas grown in a dish show how color vision develops

Posted on March 24, 2019 by Dawn Kaplan

Human retinas were grown from scratch by biologists at Johns Hopkins University to determine how cells that allow people to see color develop.

The research lays the foundation for researchers to develop therapies for eye diseases such as color blindness and macular degeneration.

“Everything we examine looks like a normal developing eye, just growing in a dish,” said Robert Johnston, a developmental biologist at Johns Hopkins. “You have a model system that you can manipulate without studying humans directly.”

Johnston’s lab explores what happens in the womb to turn a developing cell into a specific type of cell, an aspect of human biology that is largely unknown.

Johnston and his team focused on the cells that allow people to see blue, red and green — the three cone photoreceptors in the human eye.

Previously the majority of vision research has been on mice and fish, neither of these species has the dynamic daytime and color vision of humans. So Johnston’s team had to create the human eyes they needed — with stem cells.

“Trichromatic color vision delineates us from most other mammals,” said lead author Kiara Eldred, a Johns Hopkins graduate student. “Our research is really trying to figure out what pathways these cells take to give us that special color vision.”

Over several months, as the cells grew in the lab and became full-blown retinas, the team found the blue-detecting cells materialized first, followed by the red- and green-detecting ones. They found the key to the molecular switch was the ebb and flow of thyroid hormone. Important to note is the level of this hormone wasn’t controlled by the thyroid gland, which of course isn’t in the dish, but entirely by the eye itself.

“What’s exciting about this is our work establishes human organoids as a model system to study mechanisms of human development,” Johnston said. “What’s really pushing the limit here is that these organoids take nine months to develop just like a human baby. So what we’re really studying is fetal development.”

This groundbreaking work can lead to all sorts of applications is the vision deficiency arena.

To read the article in its entirety click here. https://www.sciencedaily.com/releases/2018/10/181011143112.htm

A common Diabetes medication may actually help prevent development of Macular Degeneration, a common cause of blindness

Posted on March 17, 2019 by Dawn Kaplan

According to an article published on October 29, 2018 by American Academy of Ophthalmology Researchers from Taiwan have shown that people with type-2 diabetes who were treated with Metformin showed a significantly lower rate of age-related macular degeneration (AMD).The study further suggests that the anti-inflammatory and anti-oxidative effects of metformin can protect against AMD while also controlling diabetes. The research was presented at AAO 2018, the 122nd Annual Meeting of the American Academy of Ophthalmology.

It has been long known that inflammation and oxidative stress play a key role in the development of both diabetes and AMD. Since metformin suppresses inflammation and oxidative stress, researchers in Taiwan theorized that it was possible that the diabetes drug could also protect against AMD, one of the leading causes of blindness in Americans over age 50, currently affecting about 2.1 million people in the United States alone.

The researchers used the Taiwan National Health Insurance Research Database, to collect data on all patients recently diagnosed with type 2 diabetes from January 2001 to December 2013, dividing them into two groups: Those who took metformin (45,524 patients) and those who did not (22,681 patients). After following both groups for 13 years, the researchers found that patients in the metformin group had a significantly lower risk of developing AMD. In fact, half as many patients in the metformin group had AMD compared to the control group.

“Our study is the first to reveal the protective effect of metformin on the development of AMD,” said lead investigator, Yu-Yen Chen, M.D. “While more study is required to determine just how metformin protects against the development of AMD, this is an exciting development for patients at risk.”

AMD is a degenerative disease that happens when part of the retina called the macula is damaged. It’s the part of the eye that delivers sharp, central vision needed to see objects straight ahead. Over time, the loss of central vision can interfere with everyday activities, such as the ability to drive, read, and see faces clearly.

Diabetes is a complex disease that can result from, genetics, environment, lifestyle factors, such as smoking and diet, and involve systemic diseases like heart disease. How the diabetes develops is not fully understood, but researchers have shown that oxidative stress and inflammation play a critical role in the development and progression of AMD. Drusen formation, the earliest clinical finding, has been shown to result from a localized inflammatory response.

The research on Metformin provides a hope that blindness need not be an eventuality for most people afflicted with diabetes.

Read Original Article: https://www.sciencedaily.com/releases/2018/10/181029102836.htm