Blindness can be caused by… intestinal bacteria

New research suggests that eye disease may be caused in part by bacteria that escape from the gut and land on the retina.

Previous research has shown that bacteria in the eyes is not as rare as ophthalmologists previously thought, so the study authors set out to find out whether they could cause retinal disease.

An international team of scientists has shown that eye diseases that have long beenthought to be purely genetic, may be caused in part by bacteria that leave the intestines and enter the retina. The main conclusion of scientists: these bacteria can be suppressed by treating them with antibiotics, and thereby cure an ophthalmic disease.

Hereditary retinal diseases such as retinitis pigmentosa, Affects approximately 5.5 million people worldwide. Until recently, experts believed that mutations in the Crumbs gene (CRB1) are the main cause of these severe diseasessome of which cause blindness. Now there is a “new look” at this complex problem.

Co-author Richard Lee and his colleagues found that CRB1 mutations weaken the connections between the cells lining the colon and weaken the protective barrier around the eye. This prompted study co-author Lai Wei, an ophthalmologist at Guangzhou Medical University in China, to breed mice with the CRB1 mutation but with reduced levels of bacteria. These mice showed no signs of distortion of the retinal cell layers, unlike the control group with typical intestinal flora.

Treating the mutant mice with antibiotics reduced damage to their eyes, suggesting that people with CRB1 mutations may benefit from antibiotics or anti-inflammatory drugs that reduce exposure to the bacteria. “If this is a new mechanism that can be treated, it will change the lives of many people,” says Lee.
While the paper presents a “cool idea,” people with CRB1 mutations don't need to rush into it just yet, says Jeremy Kay, a neuroscientist at Duke University Durham in North Carolina. “I'm very concerned that patients will read this and think they have a simple solution to a complex problem,” he says.

“Moving from mouse models to human clinical trials is not easy,” says co-author Richard Lee. — Bacteria can penetrate other parts of the human body, causing diseases. But bacteria are very rare in the eyes, and even a small amount of them can cause severe ophthalmic pathology.”

The study was published in the scientific journal Cell.

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