How climate change threatens eye health » Yale Climate Connections

For five months in 2017, farmworker Alka Kamble experienced blurred vision in one of her eyes but didn’t consult an ophthalmologist. “I couldn’t afford it, and neither did I have the time, as I had to work long hours to make ends meet,” she says.

Then Kamble saw a flyer for a free eye check-up clinic near her home in Jambhali village, in India’s Maharashtra state. The doctor there suggested immediate cataract surgery and said that overexposure to solar radiation had likely contributed to her deteriorating eyesight.

Kamble, now 55, had for decades worked long hours in the scorching heat without sunglasses or shade. Conditions have worsened as heat waves have intensified in India, she adds. “The heat has become so unbearable that farmers are finding it difficult even to work for two hours in the field during summers.”

A number of well-known factors, including exposure to UV radiation, genetics and aging can lead to cataracts, a condition affecting roughly 94 million people in which the lenses of the eyes get cloudy, causing blurry vision. But in recent years, researchers have found another causative factor for cataracts and other eye disorders: climate change.

Climate change is increasing risk to eye health in multiple ways. First, it is making the planet hotter — Earth’s average surface temperature in 2024 was the warmest on record. Body temperatures reaching 40 degrees Celsius (104 degrees Fahrenheit) can cause heat stroke, a condition that disrupts biological processes throughout the body. In the eyes, heat stroke damages the natural defense systems that normally counteract the buildup of harmful molecules called reactive oxygen species, explains Lucía Echevarría-Lucas, an ophthalmologist at the Hospital of La Axarquía in Spain’s Málaga province.

The eye lens is made up of crystalline proteins that must remain organized to remain transparent. Reactive oxygen species can damage these proteins, “forming opacities that lead to cataracts,” Echevarría-Lucas says.

Since the lens can’t regenerate the proteins, the more time one spends in the heat, the greater the risk of developing cataracts. In a study spanning 10 years in southern Spain, Echevarría-Lucas and her colleagues found an additional 370.8 cases of cataracts per 100,000 inhabitants for each degree Celsius rise in the maximum average temperature each year. And though the typical age of onset of cataracts is 60 or older, cataracts in people aged 15 to 49 were more common in regions where a high percentage of people work in agriculture.

Another way global warming is contributing to eye disorders is by increasing our exposure to UV radiation, according to Echevarría-Lucas and study coauthor José María Senciales González, a geographer at the University of Málaga. Some of this is driven by behavior — people tend to spend more time outdoors when it’s warm. But in some places, such as Southern California and the Costa del Sol in Spain, hot, dry winds sap from the air water vapor that would normally absorb UV radiation, causing more UV exposure. UV radiation also generates reactive oxygen species that damage the eye lens, and can directly damage the DNA of lens cells, Echevarría-Lucas adds.

Cataracts are one of the most common causes of vision impairment worldwide. But climate change is also causing an uptick in other eye conditions. These include keratitis — an inflammation of the cornea, the eye’s clear, outermost layer — pterygium, an overgrowth of fleshy pink tissue over the white part of the eye (called the sclera) and conjunctivitis, an eye infection or irritation also called pinkeye, notes Yee Ling Wong , an ophthalmologist-in-training at Manchester Royal Eye Hospital in the UK and coauthor of a 2024 overview in the Journal of Climate Change and Health.

One 2023 study of nearly 60,000 people in Ürümqi, in northwestern China, found that temperatures exceeding 28.7°C — just 83°F — increased the risk of conjunctivitis by roughly 16 percent compared to daily temperatures around 10.7°C, or 51°F. Longer pollen seasons and increased mold growth, both of which have been linked to climate change, are also contributing to an uptick in conjunctivitis caused by allergies, says ophthalmologist Malik Kahook at the University of Colorado School of Medicine.

Beyond these direct impacts, climate-driven droughts cause food insecurity that can lead to deficiencies in essential nutrients, such as copper and vitamins B12, B1 and B9 , that risk damaging the optic nerve. During droughts, people are often forced to use unsafe water, which also increases the risk of eye infections.

There are ways to protect the eyes from climate-driven damage. First and foremost, outdoor workers should be given sufficient shade and frequent breaks to cool down, says Jesús Rodrigo Comino, a geographer at the University of Granada and a coauthor of the Spanish study. He also recommends wearing a hat with a visor that shields the eyes, as well as UV-filter sunglasses: Sunglasses offer nearly 38 percent more protection than not wearing them, Rodrigo Comino says.

Contact lenses containing a hydrogel that allows more oxygen to reach the cornea can also help to stave off damage from UV, Rodrigo Comino says. These contact lenses are widely available and commonly prescribed by eye-care professionals worldwide. Eating foods rich in vitamins A, C and E, and tryptophan, as well as avoiding smoking and drinking alcohol, can also help, he adds.

Reducing greenhouse gases and ozone-depleting chemicals, which increase UV exposure, are key to protecting eye health at a global level. But even under the best climate scenarios, intense climate-driven heat, droughts, and other eye irritants will continue to affect people like Kamble.

Some programs are attempting to address the problem, including India’s National Programme for Control of Blindness and Visual Impairment, which provides access to affordable cataract surgeries. That program covered the cost of Kamble’s surgery. “I never realized that the problem could get so severe by working in the fields,” she says.

This article originally appeared in Knowable Magazine, a nonprofit publication dedicated to making scientific knowledge accessible to all. Sign up for Knowable Magazine’s newsletter.