Parental advice to stop reading under the covers has an update for the digital age.

Toronto optometrist Naeem Abdullah says he hears the question nearly every day: Does reading in dim light really worsen your eyesight?

"I think it started when people started reading under candlelight. That would have been a very difficult way to read with a flickering light," Abdullah says.

Eye exam

Bright light activates the cone photoreceptors in our eyes. (Fred Thornhill/Reuters)

His advice? "Turn the lights on because it's easier to read. It's always better to get the eye to be working under the best conditions that it can, but it doesn't do any physical damage to the eye."

Abdullah compares reading in dim light to driving a sports car in the mud instead of a street. Photoreceptors in the eyes called cones are responsible for central vision tasks like reading. Bright light activates cones. 

"When light is dim, you're using the rods more and they're not quite as sensitive as the cones," he explained. "It just causes you to work harder to do something that is quite simple."

Another question Abdullah often hears is about the strain from laptops, cellphones and other screen devices.

"When we're on computer screens, we forget to blink. Our natural tendency with our eyes is to look straight ahead, but when we read or look at a computer screen, your eyes have to turn in …. Over a prolonged period of time, it becomes quite difficult to do."

Some tips to help your eyes:

  • Remember to blink.
  • Use the 20-20-20 rule — every 20 minutes, take a 20 second break and look 20 feet ahead to force your eyes to relax before they return to their job.
  • Set colour and contrast tones to suit your eyes.
  • Minimize reflected glare on your screen.
  • Keep your screen free of fingerprints and dust.
  • Eat berries, beans, green, leafy vegetables, nuts and fish rich in omega-3 fats to nourish your eyes.

And getting a good light for a child's room won't hurt.

With files from CBC's Christine Birak