Glaucoma, which affects about 80 million people worldwide, is a group of diseases that damage the optic nerve, which carries visual information from the eye to the brain. It can lead to permanent vision loss, usually affecting peripheral vision at first and later central vision. Cataracts are even more common, affecting more than 94 million people globally; the condition occurs when the eye's lens becomes cloudy, causing blurred vision and, eventually, blindness.

Aging raises the risk of both diseases, as do certain medical conditions, such as diabetes. But now, a review of 41 studies suggests that people who are exposed to higher levels of air pollution may also face a greater risk of these diseases. The research, presented in September at the 44th Congress of the European Society of Cataract and Refractive Surgeons in London, brought together evidence from dozens of studies collectively involving millions of people across East Asia and the U.K.

The studies were observational, meaning they can only draw a link between air pollution and the eye conditions, rather than prove that air pollution causes the diseases. But still, "this reframes glaucoma and cataract as conditions shaped by where you live and breathe, not just how long you've lived," said study co-author Dr. Ahmed Alnabihi, an ophthalmologist at King Khaled Eye Specialist Hospital and Research Center in Saudi Arabia, who presented the findings. These environmental exposures may compound age-related decline in the eye as they do in cardiovascular disease, he said.

PM2.5 shows the clearest links

The researchers examined exposure to several pollutants, including different sizes of particulate matter (PM), such as fine PM2.5 and larger PM10. They also looked at nitrogen dioxide, sulfur dioxide, ozone and carbon monoxide.

Most studies included in the review estimated people's long-term exposure based on the pollution levels around their homes and in their communities. They used a range of methods, including government monitoring systems, satellite data and computer models designed to estimate pollution levels. A few studies examined short-term exposure and its relation to more sudden eye issues, such as acute angle-closure glaucoma, a medical emergency that can quickly cause vision loss.

Using this wealth of data, the team compared pollution exposure with rates of glaucoma, cataracts and age-related macular degeneration (AMD), another common eye condition that impairs vision. PM2.5 — tiny particles that measure 2.5 micrometers or smaller — showed the clearest associations with glaucoma and cataract risk.

People with the highest exposure to PM2.5 had 70% higher odds of glaucoma, compared to those with the least exposure. Plus, an increase in PM2.5 exposure equivalent to the difference between the 25th and 75th percentiles of exposure within each study was associated with 8% higher odds of glaucoma and a 4% higher hazard of cataracts.

The evidence was less consistent for air pollution and age-related macular degeneration, which damages the central part of the retina that's responsible for sharp, detailed vision. And unlike the clear connection seen with PM2.5, other pollutants showed less consistent links to eye disease. For instance, nitrogen dioxide was not significantly tied to AMD, ozone was not tied to cataracts, and neither pollutant was linked to glaucoma. Sulfur dioxide and PM10 showed no significant associations with any of the three conditions.

The association between PM2.5 and glaucoma was relatively consistent across the reviewed studies, said Nidhi Singh, an environmental epidemiologist at the IUF-Leibniz Research Institute for Environmental Medicine in Germany, who was not involved in the study. The findings for PM2.5 and cataracts were moderately consistent, albeit more variable than the glaucoma data; still, she said that the analysis seems to support a link.

Singh did caution that the underlying evidence is observational. "Therefore, the results demonstrate an association, not by themselves a causal effect of PM2.5 on glaucoma or cataract," she told Live Science.

What explains the increased risk?

The exact biological mechanisms behind these links remain unclear, but Alnabihi noted that fine particulate matter is small enough to be absorbed into the body. This can trigger oxidative stress, in which harmful molecules overwhelm natural defenses and cause damage. It also drives chronic, low-grade inflammation, in which the immune system stays mildly activated for long periods, he explained.

In the eye's lens, these processes can "damage the crystallin proteins that keep it transparent, causing them to misfold and cloud, which is what a cataract is," Alnabihi said.

In the optic nerve, the same processes are thought to damage retinal ganglion cells, a special type of neuron that relays information from the retina to the brain. This can contribute to glaucoma independent of internal eye pressure, he said, which is another big risk factor.

"Unlike the lungs or gut, its [the eye's] surface is in direct, continuous contact with outdoor air, giving pollutants a uniquely direct route that might cause damage," he added.

Other studies have found clues that support the link between PM2.5 and eye damage. Mice that were exposed to ambient PM2.5 for nine months developed elevated pressure inside their eyes, a glaucoma risk factor. The researchers observed both oxidative stress and nitrative stress — a similar phenomenon — in the tissues that drain fluid from the eye, which may help to explain the rise in pressure.

Studies of humans and human cells have uncovered similar patterns. In data from more than 480,000 people in the UK Biobank, a large repository of health information, those exposed to higher PM2.5 were more likely to develop glaucoma over time. In another study, scientists exposed lab-grown human retinal tissue made from stem cells to PM2.5. The particles disrupted retinal cell development, including that of retinal ganglion cells, while increasing cell death.

These studies offer pieces of a possible mechanism, but for now, how those pieces fit together in people remains unclear.

This article is for informational purposes only and is not meant to offer medical advice.

'> 'A uniquely direct route that might cause damage': Scientists uncover link between air pollution and eye diseases like glaucoma begin to recover until the 16th century.

The Black Death era is the perfect opportunity to look at the effects of humans on biodiversity over a longer period, Jonathan Gordon, a paleoecologist at the Leverhulme Centre for Anthropocene Biodiversity at the University of York and first author of the paper, told Live Science.

In the study, which was published March 4 in the journal Ecology Letters, the researchers compared more than 100 European pollen records that included about 4,600 samples. The records came from sites ranging from the lowlands of France and uplands of the southwest United Kingdom to the Swiss Alps.

The pollen records "give us information on the past diversity of the plant records," Gordon said.

For example, cereal grains ‪—‬ such as wheat, barley and rye ‪—‬ were a fundamental part of medieval agriculture. The representation of pollen from these types of crops in the pollen record points to historic land use.

The researchers divided the pollen data into three categories based on the presence of cereal pollen: places where agricultural production went up, places where it went down, and places where there was no evidence of cereal cultivation.

"We found a decline in biodiversity overall, but the decline overall was driven by those landscapes that declined in agricultural production," Gordon said.

"In those landscapes where agricultural production went down, there was a reduction in biodiversity of around 40%. Then, after about 150 years, as populations started recovering and landscape disturbances started increasing again, biodiversity went up to slightly above the level it was before."

Mosaic landscapes

Many people think there was a "stable and pristine world in which the entry of people has only one result: net loss of species and homogenization," Erle Ellis, an agroecologist at the University of Maryland, Baltimore County who was not involved in the research, told Live Science in an email. "The paleoecologists have always known the story is far more complicated."

There is a growing body of evidence showing that people's long-term cultural shaping of their landscapes often creates more diverse habitats, known as "mosaics," that can sustain more species than simple homogenous landscapes can, he said.

Whereas modern agriculture focuses on single crops on plots of land, in previous centuries, "you had all these different types of agriculture operating within the same landscape," Gordon said.

"In that landscape, you had lots of natural features that remained from the Middle or Early Holocene (which began after the last Ice Age about 12,000 years ago)," he added. "You had old bits of woodland, you had heaths, you had ponds, and bits of secondary forest. It was all interlaced with these agricultural mosaics, and that led to raised biodiversity because there were more habitats for different plant species to exploit."

The findings highlight the differences between medieval and modern land use practices — and their consequences for biodiversity. Research suggests that during the 20th century, global biodiversity declined by up to as much as 11% and human activities‬, such as land-use changes, pollution, and climate change‬, are the major culprits. In agriculture, the practice of monoculture — where a single crop species is grown over a large area — reduces biodiversity.

"What this work contributes to showing is that, until relatively recently, even in Europe, very different forms of land management and interaction were practiced than exist today," Patrick Roberts, director of Department of Coevolution of Land Use and Urbanisation at the Max Planck Institute of Geoanthropology, told Live Science in an email.

"Rather than the monoculture, plantations, or uniform changes to landscapes we see in the 20th and 21st centuries, emphasis was placed on maintaining 'mosaics,'" said Roberts, who was not involved in the new research.

In the study, "we can see how relationships between people and biodiversity have changed through time and how people can actively use landscapes while maintaining biodiversity and mixed ecosystem functions," he said.

There is still more to understand about how humans' disappearance from landscapes in the Black Death era affected the natural world, Gordon said. "There are a lot of other types of diversity ‪—‬ not just the number of types, but what the different types present actually do." There may be a hundred types of plants in a landscape, but if they do the same thing, "you have low functional diversity," he said.

Functional diversity "is super important for how ecosystems adapt to changes in climate and how resilient they are, which is something we need for future-proofing our agricultural system," Gordon said.

'> Black Death had dramatic effect on species diversity as humans abandoned farmland, study finds Timothy Cunningham, an assistant professor of astronomy and astrophysics at the University of Warwick who led an international team of researchers to study the object, said in a statement.

SN 1181 is one of only five supernovas in the Milky Way galaxy known to have been witnessed from Earth before the invention of the telescope. (Those optical instruments first appeared in the Netherlands in 1608.) Now, advanced ground-based telescopes can produce wonderfully detailed images of those historic remnants. This latest image is from the Gemini North telescope on Mauna Kea in Hawaii and reveals about 10 times more filamentary structures in Pa 30 than have been seen before. This extraordinary detail gives astronomers fresh clues about the unusual explosion and the environment surrounding the star.

"These images give us the clearest picture yet of Pa 30's structure, and it's not what we expected," said Cunningham, whose team published their findings in The Astrophysical Journal. "The filaments are made of chains of tiny knots rather than smooth streaks, providing new constraints on the nature of the space around the star before it exploded and the physical processes that have shaped the expanding ejecta."

The knot-like structures may have resulted from variations in temperature or density in material surrounding the star as debris from the explosion expanded.

Pa 30 contains another unusual feature: a surviving star that sits almost exactly at the center of the remnant. That's highly unusual, because a supernova explosion typically sends stars away from their original positions. It suggests that the original explosion was highly symmetrical, the researchers said.

Furthermore, Pa 30 is thought to be a Type Iax supernova. Unlike standard Type Ia supernovas, which destroy their stars, a Type Iax event is a lower-energy, incomplete explosion of a white dwarf star that can leave behind a remnant known as a "zombie star." It's the only Type Iax supernova ever found.

'> This 850-year-old 'firework' supernova is full of mysterious knots

A calculated hunter

Cuttlefish are visual hunters, using their large, complex eyes to locate and track potential meals. In general, their strategy involves a slow, stealthy approach, said Bret Grasse, the manager of cephalopod operations at the Marine Biological Laboratory in Woods Hole Massachusetts.

"The cuttlefish will slowly approach the prey so as to not alert the unsuspecting shrimp, fish or crab," Grasse told Live Science in an email.

During their approach, cuttlefish often put on a showy display, producing moving bands across their body. These displays are produced by a combination of light-reflecting pigment cells known as iridophores, leucophores and chromatophores. These cell types contract and expand to produce specific colors and patterns, all within milliseconds.

Some may wonder whether this trick can mesmerize prey, but scientists don't think that's the case.

Hypnosis, defined as a mental state of increased relaxation and altered awareness, is thought to be a uniquely human psychological state. There is very little research on whether fish can be hypnotized, but a 2005 study found that pushing a steady stream of water through the snapper (Chrysophrys auratus) put them in an immobile state similar to being hypnotized. Another study looked at sedative hypnotic drugs like benzodiazepines and barbiturates and their effects on zebrafish, finding that the fish had molecular receptors for these drugs, which helped render them immobile. However, whether fish can be visually put into a state like hypnosis has yet to be directly studied.

And while some animals, such as chickens, can be induced into trance-like conditions of tonic immobility, an involuntary, temporary state of unresponsiveness that happens when humans or animals experience extreme trauma, it's unlikely that the cuttlefish's color changes "hypnotize" their prey, Connor Gibbons, the cephalopod facility manager at Columbia University told Live Science. Instead, some researchers believe that the color show serves as an ingenious disguise.

As waves of different colors ripple down the cuttlefish's body, the shape of the animal becomes less obvious to its prey, so they may not see the cuttlefish as a threat to flee from, Gibbons said.

"It's only part of something looming at them, which they're like, 'I don't know if you are a predator? Are you just passing waves? What are you?'" Gibbons said. "And then by that time, it's too late."

Once they get close enough, the cuttlefish shoots their two long, specialized feeding tentacles from small hidden pouches near the animal's mouth at their prey.

"The closest thing I can compare it to is the tongue of a chameleon extending out to grab an unsuspecting insect," Grasse said. "Cuttlefish feeding tentacles will fire out in the blink of an eye before the prey can react and escape."

Then, the prey is pulled toward the cuttlefish's mouth, pierced by its sharp, chitinous beak and injected with venom. The use of the venom helps the cuttlefish reduce their energy usage when hunting "as the cuttlefish does not want to use unnecessary energy and struggle against the prey while it's trying to eat," Grasse said.

However, the notion that cuttlefish flash colors to hide their body shape is only one idea of why cuttlefish perform these strobing color displays. Other researchers, including Grasse, describe them as a way to distract their prey.

"Essentially, they are trying their best not to alarm the prey to their presence," he said. By breaking up the size of their bodies, cuttlefish can convince their prey they're not as large or alarming as they may seem.

Whether the light shows are for disguise or distraction still needs parsing out, Gibbons said, and scientists also need a better understanding of how the cuttlefish controls its deadly dermal display. "The jury is still out on exactly what is happening," he said.

How much do you know about octopuses? Find out with our octopus quiz!

'> Can cuttlefish hypnotize their prey? historically mild weather. In recent decades, their range has contracted significantly. But climate change is threatening the health and function of these forests.

The region has seen significant warming in recent decades, and faces more frequent extreme heat days, with temperatures spiking above 100 degrees Fahrenheit (37 degrees Celsius). Now, in a new study, published Sept. 22 in the journal JGR Biogeosciences, a team of researchers has shown that California's renowned redwoods are struggling to photosynthesize in the heat.

Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. It chemically converts carbon dioxide and water into sugars and oxygen.

"These trees adapted to grow in really temperate environments, so no one had really looked at the impact of heat on photosynthesis," study first author Lily Klinek, a doctoral candidate in the Plant Optics Lab at the University of California, Davis, told Live Science.

From 2022 to 2024, Klinek and colleagues measured how the leaves of redwoods in Garcia River Forest in Mendocino County responded to the heat. Once or twice a month, the researchers took three different California redwood leaf samples and measured their fluorescence and temperature.

A plant's molecules can use absorbed light in three ways: for photosynthesis, dissipated as heat, or reflected as light (florescence). Fluorescence is a proxy measurement to understand photosynthesis in the plant, Klinek said.

The researchers wrapped a fourth leaf in tinfoil for 20 minutes to put it in a state of "rest" before taking the same measurements. "When they're in a state of rest, we expose them to a pulse of light that’s in the wavelength they would use for photosynthesis to see what would be their maximum photosynthetic rate," Klinek said.

They found that on hot days, the leaves exposed to sunlight were up to 18 degrees Fahrenheit (10 degrees Celsius) hotter than the air temperature. "That's a huge difference and indicates that the leaves are stressed to the point where they can't thermoregulate effectively," Klinek said.

Many plants' leaves manage their temperature and photosynthesis by opening or closing their stomata, which are tiny pores on their surface. These stomata (from the Greek word for mouth) regulate the amount of carbon dioxide entering the plant, and how much oxygen and water vapor it releases. Lower carbon dioxide intake leads to reduced photosynthesis, meaning the plant has less energy.

The large differences between air and redwood leaf temperatures suggest that the leaves had closed their stomata to avoid losing water from evaporation during hot conditions and consequently overheated, Klinek said.

To further investigate the impact of heat on leaf physiology, the researchers took California redwood leaf samples back to the laboratory and exposed them to a range of temperatures while they were in water. Despite their access to water, the leaves still photosynthesized less as they got hotter, even though their stomata were open, Klinek said.

This shows that heat imposes direct limitations on redwood photosynthetical capacity, rather than indirectly decreasing that capacity by causing stomatal closure, the researchers wrote. The finding indicates that redwoods' ability to photosynthesise and store carbon will decrease as temperatures rise.

​​"It is not only stomatal closure that is causing reduced photosynthesis," Lucy Rowland, an ecologist at the University of Exeter in the U.K. who was not involved in the study, told Live Science in an email. "These trees are already suffering from the direct effects of heat on their photosynthetic systems."

The finding has serious implications for the future of redwoods and similar plants. "The points at which this damage becomes irreversible remains really poorly understood, but is something which is really essential to understand if we want to predict how our future climate is going to impact plants," she said.

The next step in Klinek's research is to move beyond leaf physiology to understand these thresholds on the trees and their ecosystems as a whole.

"We're not sure to what extent the effect that we saw is a reversible stress response and if they are sustaining damage from this constant stress," she said. Researchers need more data to "really get a better sense, beyond the leaf scale, how these ecosystems are responding to heat and drought," she added.

'> California redwoods are struggling in the heat — and it's not clear how much damage is being done