Good quality sunglasses or goggles with side protection and an eye protection factor (EPF) of at least 10 are essential and should be worn throughout the day. Reflected sunlight from snow can lead to painful and dangerous snowblindness if goggles are not worn. Even on dull days it is possible to get severe headaches. Straps for keeping glasses in position are available, and they can prevent loss or damage to the glasses in falls. Double-lens goggles are less prone to fogging up, but are more expensive. Many experts suggest goggles are better for poor weather and sunglasses are better for sun.