During summertime activities, one specialist has simple advice: Protect your eyes.

Common leisure pursuits (and the outdoors itself) can pose severe and permanent risks to your vision.

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"You get two eyes in life; there is no eye transplantation," says Theresa Cooney, M.D., a clinical assistant professor of ophthalmology and visual sciences at the University of Michigan Kellogg Eye Center. "Once you hurt your eye, that's what you live with."

Cooney spoke more about the dangers that peak during warmer months.

Because we can't put sunblock on our eyes, a combo of quality sunglasses (make sure they block UVA and UVB rays) and a wide-brimmed hat are necessary shields against major risks. "Your eyelids are prone to skin cancer, as the sun bounces off your nose," Cooney says. Sun exposure, she adds, has been shown to cause and accelerate cataracts and macular degeneration.

It might dazzle a crowd, but setting off fireworks simply isn't worth the show. Says Cooney: "There can be a pretty severe blast that can burn and completely destroy the eyes." Some of the most serious summer eye injuries are tied to fireworks, she says. Nationwide, such incidents doubled in 2014 compared with two years prior, according to the American Academy of Ophthalmology.

Contacts and swimming can be an unsafe combination. Lenses "act like a sponge and hold water," Cooney says. That's a problem if the water — be it fresh or chlorinated — harbors bacteria or parasites. One such hazard is Acanthamoeba, which in rare cases can cause infection and blindness. It is safest to swim without contact lenses. Otherwise, wear ones that can be disposed of immediately after swimming and rinse your eyes afterward. Also consider wearing goggles with a good seal around the eyes.

Lawnmowers and weed trimmers simplify outdoor upkeep. But the powerful machines can cause dangerous momentum. "When those blades move, they shoot things out — including stones," says Cooney, who notes that a punctured eye is a common resulting injury. Avoid this scenario by wearing protective goggles with shields when working in the yard.

Any small ball that can fit into the eye socket presents an issue. "We're talking mostly baseballs, racquetballs, tennis balls, anything that comes at a high velocity," says Cooney. While such impact probably won't put a hole in the eye, it can create retinal damage or a hyphema, a pooling of blood between the cornea and iris. That, Cooney says, can cause glaucoma and vision loss.