Vision: Where is the suspected location on the body for eye conditions that lead to blindness

Could the health of the eyes be related to the functioning of the intestine? A recent study reveals a unique correlation and the role played by the gut microbiota

Recent findings create hope that antibiotics could potentially treat certain genetic diseases that can lead to blindness.

For genetic eye conditions that lead to blindness, according to a recent study published in Cell, bacteria that escape from the intestine and “travel” to the retina may also be implicated. Until recently, specialists estimated that the eyes are usually protected by a layer of tissue that bacteria cannot penetrate. Therefore, these results are “unexpected” according to Dr. Martin Kriegel, a microbiome researcher at the University of Münster in Germany, who was not involved in the study. “This is a major shift in the paradigm we knew until now,” he adds.

Inherited diseases of the retina, such as retinitis pigmentosa, affect about 5.5 million people worldwide. Mutations in the Crumbs homolog 1 (CRB1) gene are the primary cause of these diseases, some of which lead to blindness. Previous studies have shown that bacteria are not as rare in the eyes as ophthalmologists previously believed, leading the authors of the study to wonder if bacteria cause diseases of the retina, says co-author Dr. Richard Lee, an ophthalmologist then at University College London.

As Dr. Lee and his colleagues found, mutations in CRB1 weaken the bonds between the cells lining the intestine, in addition to the role they have long observed in weakening the protective barrier around the eye. This conclusion prompted the study’s co-author, Dr. Lai Wei, an ophthalmologist at Guangzhou Medical University in China, to create mice with CRB1 mutations with reduced levels of intestinal bacteria. These mice did not show signs of distortion of the cellular layers in the retina, unlike those with typical gut flora.

How Fires Affect the Eyes – Irritations and Inflammations of the Eyes that Impact Vision.

Over the past decade, devastating forest fires have struck Australia, Europe, and America, exposing millions of people to their toxic smoke. This has consequences for the human body, with the eyes, which have direct contact with their surface, being one of the first organs affected.

“The smooth function of the eye’s surface (ocular surface) is crucial for vision. However, it is not a single entity but consists of individual structures, each of which can be affected by smoke,” says Dr. Anastasios-I. Kanellopoulos, MD, Ophthalmic Surgeon, founder and Scientific Director of the LaserVision Ophthalmology Institute, Professor of Ophthalmology at the University of New York.

The ocular surface is composed of the corneal epithelium, the conjunctiva, the tear film, the eyelids, and glands that produce various components of the tear film.

The movement of the eyelids stimulates the production of tears, which coat the cornea and conjunctiva. This ensures their adequate hydration, nourishment, and protection from pathogenic microorganisms and toxins.

Anything that disrupts the balance of this system can lead to eye irritation and inflammation that affect vision.

The smoke from forest fires consists of thousands of components, including solids (molecules, heavy metals, organic microorganisms, etc.), vapors, and complex mixtures of gases such as carbon monoxide, sulfur dioxide, nitrogen oxides, ozone, etc. It may also contain volatile compounds, microscopic suspended particles, and more. Additionally, because forests are often near buildings, businesses, or infrastructure that may burn, smoke from forest fires can contain many other chemicals and toxic compounds.

Exposure of the ocular surface to all these components can cause symptoms in both the personnel trying to extinguish the fires and the general population. Moreover, it’s not just the residents of affected areas who are at risk, but people hundreds of kilometers away, as smoke from forest fires can cover vast distances, driven by strong winds.

“Many people experience eye irritation and inflammation from wildfires. This is even more likely to occur in those who already have eye disorders such as dry eye, blepharitis, or allergic conjunctivitis,” notes Dr. Kanellopoulos. “Irritation and inflammation from smoke can cause a burning sensation, stinging in the eyes, redness, and increased tear production (tearing). Patients may also feel a foreign body sensation in their eyes, dryness, and grittiness.”

Especially in areas with heavy smoke, some patients may experience changes in their vision (e.g., blurriness), irritation of the conjunctiva, or, more rarely, severe dry eye that damages the corneal surface and affects visual acuity.

Furthermore, with prolonged exposure to smoke from forest fires, intense inflammation of the conjunctiva can occur, promoting the formation of scars. These scars can lead to a condition called trichiasis, where eyelashes grow inwards (towards the eyeball), constantly touching and irritating the conjunctiva or cornea.

When smoke from fires has a high concentration of microscopic suspended particles, it can reduce vision by causing severe eye irritation. These particles can also trigger allergic reactions.

Smoke from wildfires can cause significant discomfort for contact lens wearers, as it can get trapped between the lenses and the eyes, causing inflammation and pain.

“Fortunately, the effects of smoke from forest fires on the eyes appear to be temporary. However, we do not know if the repeated exposure to smoke, which we have been experiencing in recent years, will have long-term consequences,” emphasizes the professor. “We know that those living in areas with high levels of atmospheric pollution have a significantly increased likelihood of developing dry eye and long-term serious conditions such as glaucoma and age-related macular degeneration. However, this data comes from studies on atmospheric pollution from sources such as the combustion of fossil fuels and industrial processes. Special research is needed to determine if and what kind of long-term consequences the exposure of the eyes to airborne toxic pollutants from forest fires may have.”

This does not mean that we are defenseless against potential risks. To protect ourselves when there is smoke from a forest fire in the atmosphere, the first thing we should do is enter an indoor space with closed doors and windows. If you have air conditioning with HEPA air filters, you can use it to refresh the indoor air without the smoke particles.

If you have pre-existing ocular surface conditions (e.g., dry eye, conjunctivitis), do not go outside at all. To protect and relieve your eyes, use artificial tears. Patients with eye conditions who are already using them may need to increase their application (up to twice the usual amount) until the atmosphere is clear of smoke.

If it’s necessary to go outdoors, wear glasses that cover your face well to reduce the airflow entering your eyes.

Finally, if you wear contact lenses, “make sure you strictly adhere to hygiene and replacement rules. However, if the fires continue, you may need to wear your corrective glasses for a while,” concludes Dr. Kanellopoulos.