UV and Your Eyes: Cataracts, Pterygium, and the Sunglasses You Actually Need
UV damage to eyes accumulates silently for decades. The evidence linking UV to cataracts, macular degeneration, and how to pick real UV-blocking sunglasses.
The World Health Organization estimates that 20 percent of cataracts globally are caused or worsened by UV exposure. Unlike skin, the eye has no visible warning — damage compounds silently over decades until vision starts to fail.
How UV damages the eye
UVB is absorbed by the cornea and lens. Chronic exposure accelerates cataract formation (clouding of the lens), causes pterygium (a growth of tissue over the cornea), and contributes to macular degeneration. Acute high-dose UV — snow reflection, welding without protection — produces photokeratitis, the painful 'sunburn' of the cornea.
What to look for on sunglass labels
UV400 — blocks 99 to 100 percent of UVA and UVB
'Blocks 100 percent UV' or 'meets ANSI Z80.3'
Category 3 lenses for bright conditions, Category 4 for glaciers or open water
Wraparound frames — block reflected UV from below and the sides
Kids need UV sunglasses too
Children's lenses are more transparent to UV than adult lenses, so more UV reaches the retina. The American Academy of Ophthalmology recommends UV-blocking sunglasses from infancy for bright outdoor exposure.
Key takeaways
UV drives cataracts, pterygium, and macular degeneration.
UV400 or 'blocks 100 percent UV' is the label to check.
Kids need UV sunglasses; their lenses transmit more UV.
How to read this UV and Your Eyes: Cataracts, Pterygium, and the Sunglasses You Actually Need page
The UV index is a measure of erythemal (skin-reddening) irradiance, where each whole point equals 25 mW/m² of UV energy reaching the surface. That is why burn-time estimates fall roughly by half when the index doubles.
UV strength on this page follows solar elevation, ozone thickness, cloud cover, altitude, and surface reflection. Snow can bounce back most of the UV that hits it, water and sand far less, but all of them add to the dose skin receives.
Plan outdoor blocks around the peak UV window, usually between 10am and 4pm local time. Shade, UPF fabric, a wide-brim hat, and UV-blocking sunglasses reduce dose more reliably than sunscreen alone.
Cloud cover is not protection. Thin or broken cloud can still pass most incoming UV, and light cloud edges can briefly scatter more UV toward the ground than a clear sky.
Cumulative dose drives photoaging and long-term skin damage more than any single day. Small daily exposures on commutes, walks, and driving add up across a season.
UV scale reference
The WHO scale groups UV 1-2 as low, 3-5 as moderate, 6-7 as high, 8-10 as very high, and 11 or above as extreme. Protection is recommended from UV 3 upward, and shade during the middle of the day becomes the priority from UV 8 upward.
A practical routine at moderate-to-high UV is roughly one ounce of broad-spectrum sunscreen for full-body coverage, applied 15 minutes before going out, then reapplied on schedule. Clothing, hats, and shade carry the rest of the load, especially for children and anyone with a history of easy burning.
Keep exploring DermUV
These pages give more depth around uv and your eyes: cataracts, pterygium, and the sunglasses you actually need, from UV-scale reference material to calculators and city forecasts.