If you're feeling sleepy or irritable, or suffering from headaches during the workday, there may be a reason you haven't considered--your lighting. Most of us don't think much about lighting so long as we have enough to easily see what we're doing. But poor workplace lighting--which is not the same as dim lighting--can cause headache, neck soreness, and even double vision. "Lighting not only affects visual conditions, it also has an effect on our biological functions and emotions," says Michael Helander, CEO and co-founder of OLED company OTI Lumionics.

It's worth taking a few moments to think about your workplace lighting, since a few relatively minor adjustments can make a big difference to your well-being and even your productivity. Here are some steps to consider.

1. Turn overhead lights down. (Yes, you read that right.)

Most workplaces are at about double the lighting level recommended by OSHA, Helander notes. It turns out most of us don't know what level of lighting is good for us. "The human eye is very bad at determining actual levels of light," Helander says. "The way we see light is based on the amount of contrast between different types of light in our environment; we use comparisons to comprehend light levels. For instance, if the hallway outside your office is more lit up than the office itself, you might start to feel like the office isn't bright enough even though the level of brightness is the same as it's always been."

On top of that, we have a tendency to think that when it comes to lighting, more is better. "North Americans tend to push for a lot of light--we want big, powerful, bright lights because they make us feel safer," he says. "Our perception is that more light means we can see things and understand the world around us better, when in fact the opposite is true. Too much light creates 'disability glare' which makes it more difficult to see things as opposed to allowing us to see more clearly."

2. Make lighting more flexible.

Not only are we generally getting more light than we should, the amount of light that's best varies from person to person and from task to task. "For example, someone working with physical documents will have very different lighting needs than someone working with multiple computer screens," Helander says.

The best solution is to allow for variable lighting--a good reason to dim overhead lights and provide individual lights or lamps that can be turned off or on according to individual preference and task. This has the added appeal of saving electricity since you're no longer lighting space that isn't being used.

3. Reduce blue light.

"Many office environments rely on fluorescent and LED lights which give off blue light," Helander says. Blue light occurs in nature and boosts attention and mood during the morning and early afternoon. The only problem is that when we work past sunset and continue to be bombarded with blue light because too much of it disrupts sleep cycles.

To solve this problem, look for lighting options with less blue light. You might also consider wearing blue light-blocking glasses, especially since computers and other lit screens emanate blue light as well. Finally, if (like me) you tend to use your phone or tablet right before falling asleep, consider installing a blue light-blocking app. There are many available for free.

4. Consider OLED lighting.

OLED (organic light-emitting diode) is more familiar as the technology behind high-end tablets, but it's being used to create flat-panel lighting that is easier on the eyes and often more attractive than traditional lightbulbs. Unfortunately, it's also pricier, but prices are coming down, according to Helander and others in the industry.

5. Use natural light as much as you can.

You won't be able to depend entirely on natural light in most office situations. For one thing, you won't be able to get all the light you need through the window, depending on weather and time of day. And you'll likely want to work some times when it's dark outside.

Still, using natural light as much as is practical may reduce the likelihood of eye strain and related issues. After all, sunlight is what our eyes evolved to see.