"I wish people would just take a boring book -- an old-fashioned book -- and [read] by a lamp. Make sure that it's not too bright -- just so you can read," said Alon Avidan, associate director of the Sleep Disorders Center at UCLA. "And if they do that, I think they'll feel a lot better and they'll be able to relax."

These concerns stem from the fact that people are biologically wired to be awake when the sun is out.

When receptors in our eyes are hit with bright light for an extended period of time, they send a message to the brain saying it's time to be awake. The brain, in turn, stops secreting a hormone called melatonin, which makes people sleepy and helps regulate the internal sleep clock.

Normally, our brains start giving us that hormonal sleep aid at about 9 or 10 p.m. But if bright lights are shining in our eyes, that may not happen as planned. That's what worries some sleep researchers.

To make matters worse, our eyes are particularly sensitive to blue light, which is common during the day, but is less so in the evening. The fact that computer screens and phones tend to put out a lot of blue light could intensify the screen's awakening effects, even if the light isn't all that bright.

There's no exact formula for determining how much light is needed to reset a person's internal clock. Several factors are at play, including how bright the light is, what hues are present, how large the light source is, how far it is from the person's eyes and what that person tends to do during the day.

A farmer who is exposed to sunlight all day long would likely be less sensitive to artificial light at night than a person who works in a dimmer office environment, said Mariana Figueiro, an assistant professor and director of the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, New York.

While there has been research to show that light -- even artificial light -- can affect human melatonin production, no research has been done specifically on whether the iPad and laptops disrupt sleep cycles.

Some researchers are skeptical of the link.

"I don't think it's an area of concern. I think it's an area of personal preference," said Mary Lou Jackson, director of vision rehabilitation at the Massachusetts Eye and Ear Infirmary, which is affiliated with Harvard Medical School.

People shouldn't be concerned about reading on backlit electronic devices at night unless they're experiencing insomnia, in which case they should dim the screen, Jackson said.

Several iPad owners contacted by CNN said they enjoy reading on the device before bed and haven't noticed sleep problems.

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