MYTH: Reading in dim light damages your eyes.

FACTS: This old wives’ tale has been scientifically debunked. Insufficient light simply causes eye muscles to get very tired because they have to work harder to focus, says Thomas Steinemann, M.D., a media spokesperson for the American Academy of Ophthalmology. “You are not doing damage to your eyes; your eyes just may feel cramped or strained,” he says.

That’s not to trivialize the importance of proper lighting. People over age 40 often begin to lose their ability to focus, which is why many of them get glasses. Reading in dim lighting adds to their vision challenge.

Proper lighting is especially important for people with conditions that impede vision—macular degeneration, cataracts, glaucoma or diabetes, says Rachel Bishop, M.D., of the National Eye Institute.