Many things can worsen your eyesight, from everyday habits like prolonged screen use and skipping sunglasses to chronic conditions like diabetes and high blood pressure. Some of these factors cause temporary strain that resolves on its own, while others lead to permanent, irreversible damage. Understanding the difference helps you protect the vision you have.
Too Little Time Outdoors
Spending most of your day indoors is one of the clearest risk factors for developing nearsightedness, especially during childhood. Researchers project that 52% of the world’s population will be nearsighted by 2050, up from 27% in 2010, and the surge is closely tied to indoor lifestyles. Each additional hour a child spends outdoors per week reduces the odds of developing myopia by 2% to 5%. The protective effect comes from natural light itself, not from physical activity, which is why even outdoor reading or sitting appears to help.
For children, the practical threshold is roughly 11 to 14 hours of outdoor time per week, or about 1.5 to 2 hours a day. Schools that added a minimum of one hour of outdoor recess saw measurable reductions in new myopia cases. Adults who are already nearsighted won’t reverse it by going outside, but children whose eyes are still developing have a genuine window of prevention.
Prolonged Screen Use
Hours of close-focus work on phones, tablets, and computers causes digital eye strain: blurry vision, headaches, dry or burning eyes, and neck pain. The core problem is that your eyes’ focusing muscles lock into a near-focus position and struggle to relax. Over extended periods, this can shift your resting focus point closer, contributing to nearsightedness progression in younger people.
The good news is that digital eye strain is temporary and reversible with breaks. The commonly recommended approach is the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds. Proper lighting, reducing screen glare, and consciously blinking more often also help. You blink significantly less while staring at a screen, which dries out the surface of your eyes and amplifies discomfort.
One concern you may have heard about is blue light from screens causing permanent retinal damage. Lab studies do show that high-intensity blue light harms retinal cells in culture dishes and animal models. But that correlation has not been validated in human studies. The long-term impact of chronic exposure to artificial blue light on retinal health is still unclear, so the bigger, more evidence-backed worry remains eye strain and its contribution to nearsightedness, not retinal destruction.
High Blood Sugar
Chronically elevated blood sugar is one of the most damaging things that can happen to your eyes. It triggers a cascade of oxidative stress inside the tiny blood vessels of the retina: excess reactive oxygen species damage cell membranes, impair mitochondria, and cause retinal cells to die. Over time, those damaged capillaries leak fluid or become blocked entirely, starving parts of the retina of oxygen. The body tries to compensate by growing new blood vessels, but these replacement vessels are fragile and prone to bleeding, which can cause sudden, severe vision loss.
This process, called diabetic retinopathy, is the leading cause of blindness in working-age adults. It often produces no symptoms in its early stages, so people with diabetes can lose significant retinal function before noticing any change in their vision. Tight blood sugar control slows or prevents progression substantially.
High Blood Pressure
Sustained high blood pressure damages the retina through a different but equally serious mechanism. The small arteries in the retina gradually narrow and harden, reducing blood flow. As the condition progresses, those vessels begin to leak, producing tiny hemorrhages and areas of swelling visible on an eye exam. At severe levels, typically above 180/120 mm Hg, the damage can include swelling of the optic nerve itself, which threatens permanent vision loss.
The progression is gradual. Early-stage changes involve mild narrowing that you wouldn’t notice. By the time symptoms like blurred vision appear, the damage is often moderate to advanced. Because the retina’s blood vessels closely mirror the vessels in the rest of your body, an eye exam can sometimes reveal high blood pressure before other symptoms do.
Smoking
Smokers are two to three times more likely to develop cataracts and up to four times more likely to develop age-related macular degeneration compared to nonsmokers, according to the FDA. Cataracts cloud the lens, making vision progressively hazy. Macular degeneration destroys the central part of the retina, erasing the sharp, straight-ahead vision you need for reading, driving, and recognizing faces.
The damage comes from both the toxic chemicals in cigarette smoke and the reduced blood flow that smoking causes throughout the body, including the delicate vessels feeding the eye. Quitting at any age reduces the risk, though it takes years for the elevated odds to fall back toward those of a nonsmoker.
UV Exposure Without Protection
Ultraviolet radiation from sunlight directly damages two structures in the eye. UVB rays are mostly absorbed by the cornea, where intense short-term exposure causes a painful sunburn-like condition called photokeratitis. UVA rays penetrate deeper and, over years of cumulative exposure, oxidize the proteins inside the lens. Those oxidized proteins clump together, lose their transparency, and eventually form cataracts.
The lens naturally yellows with age as UV-damaged compounds accumulate. Wearing sunglasses that block both UVA and UVB significantly slows this process. A wide-brimmed hat helps too, since UV light reflects off water, sand, and pavement at angles that bypass glasses from the sides.
Vitamin A Deficiency
Vitamin A is essential for producing the pigments your retina needs to detect light. When levels drop low enough, the first symptom is night blindness: difficulty seeing in dim conditions. If the deficiency continues, the surface of the eye dries out, a condition called xerophthalmia. The World Health Organization describes a clinical spectrum that progresses from night blindness to dry, whitish patches on the eye, then to corneal drying, ulceration, and in the worst cases, softening and destruction of the cornea that leads to permanent blindness.
Severe vitamin A deficiency is rare in developed countries but remains a major cause of preventable blindness in parts of Africa and South Asia, particularly among children and pregnant women. In well-nourished populations, the more relevant concern is ensuring adequate intake of vitamin A through foods like eggs, dairy, orange and dark-green vegetables, and liver.
How Often to Get Your Eyes Checked
Many of these conditions damage vision silently for years before you notice anything wrong. The American Optometric Association recommends the following schedule for people without symptoms or known risk factors:
- Infants: First exam between 6 and 12 months
- Children 3 to 5: At least one exam during this period
- Children 6 to 17: Before first grade, then annually
- Adults 18 to 64: At least every two years
- Adults 65 and older: Annually
If you have diabetes, high blood pressure, a family history of glaucoma or macular degeneration, or have had refractive surgery like LASIK, annual exams are recommended regardless of age. Early detection is the single most effective way to prevent permanent vision loss from conditions that would otherwise progress unnoticed.