UV light and your eyes
The sun emits UV rays which penetrates through clouds, so even when the day is overcast there is still a risk of UV damage.
UV lights are stronger at altitude, in wide open spaces and on reflective surfaces. This is why often skiers and surfers wear protective goggles or sunglasses.
The radiation from UV light can increase your risks of developing eye disease including macular degeneration, cataracts and photokeratitis (snow blindness)
To avoid damage to your eyes always ensure you check the UV index and protect yourself accordingly.