Blue Light: Bad for Your Eyes?

On this page: What is blue light? • Seven key points about blue light • Blue light filters and protective eyewear

Visible light is much more complex than you might think.Stepping outdoors into sunlight; flipping on a wall switch indoors; turning on your computer, phone or other digital device — all of these things result in your eyes being exposed to a variety of visible (and sometimes invisible) light rays that can have a range of effects.

Most people are aware that sunlight contains visible light rays and also invisible ultraviolet rays that can tan or burn the skin. But what many don’t know is that the visible light emitted by the sun comprises a range of different-colored light rays that contain different amounts of energy.

Shared by www.opticianonline.net 

What Is Blue Light?

Sunlight contains red, orange, yellow, green and blue light rays and many shades of each of these colors, depending on the energy and wavelength of the individual rays (also called electromagnetic radiation). Combined, this spectrum of colored light rays creates what we call “white light” or sunlight.

THE LIGHT SPECTRUM

 

Without getting into complicated physics, there is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Light rays that have relatively long wavelengths contain less energy, and those with short wavelengths have more energy.

Rays on the red end of the visible light spectrum have longer wavelengths and, therefore, less energy. Rays on the blue end of the spectrum have shorter wavelengths and more energy.

The electromagnetic rays just beyond the red end of the visible light spectrum are called infrared — they are warming, but invisible. (The “warming lamps” you see keeping food warm at your local eatery emit infrared radiation. But these lamps also emit visible red light so people know they are on! The same is true for other types of heat lamps.)

On the other end of the visible light spectrum, blue light rays with the shortest wavelengths (and highest energy) are sometimes called blue-violet or violet light. This is why the invisible electromagnetic rays just beyond the visible light spectrum are called ultraviolet (UV) radiation.

UV rays have higher energy than visible light rays, which makes them capable of producing changes in the skin that create a suntan. In fact, the bulbs in tanning booths emit a controlled amount of UV radiation specifically for this reason.

But too much exposure to UV causes a painful sunburn — and even worse, can lead to skin cancer. These rays also can cause sunburned eyes — a condition called photokeratitis or snow blindness.

But ultraviolet radiation, in moderation, also has beneficial effects, such as helping the body manufacture adequate amounts of vitamin D.

Blue light contributes to digital eye strain; computer glasses that block blue light may increase comfort.

Generally, scientists say the visible light spectrum comprises electromagnetic radiation with wavelengths ranging from 380 nanometers (nm) on the blue end of the spectrum to about 700 nm on the red end. (By the way, a nanometer is one billionth of a meter — that’s 0.000000001 meter!)

Blue light generally is defined as visible light ranging from 380 to 500 nm. Blue light sometimes is further broken down into blue-violet light (roughly 380 to 450 nm) and blue-turquoise light (roughly 450 to 500 nm).

So approximately one-third of all visible light is considered high-energy visible (HEV) or “blue” light.

Key Points About Blue Light

Like ultraviolet radiation, visible blue light — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers. Here are important things you should know about blue light:

1. Blue light is everywhere.

9 Tips On How To Buy Prescription Glasses

How do you buy the right pair of prescription glasses for your needs?
Common issues people face are glasses are:

1. Expense – Prescription glasses can cost hundreds of dollars
2. Time – Finding the perfect pair at a fair price can take a lot of time, especially if you shop around for a particular style at a great price.
3. Confusion – What’s the right style for your face shape and profession? Do you need the add-ons and do you need multiple pairs?

My goal is to help clear up the process of buying prescription eyeglasses.

<Below are 9 tips on how to buy prescription glasses effectively>

1. Have An Up-To-Date Eyewear Prescription

The standard validity of a prescription is 2 years for adults and 1 year if you are younger. If your prescription is outdated, visit your local optical shop to get a new one.

When you get your eyesight examined, the optometrist must give you a copy of the prescription whether or not you ask for it.

Here are some abbreviations and terms listed on your prescription you’ll need to be aware of when ordering glasses online:

• OD (Oculus Dexter) refers to your right eye.
• OS (Oculus Sinister) refers to your left eye.
• Sphere (SPH) indicates the amount of lens power, prescribed to correct nearsightedness (-) or farsightedness(+).
• ADD (for bifocals) is the added magnifying power applied to the bottom part of multifocal lenses to correct presbyopia.
• Cylinder (CYL) indicates the amount of lens power for astigmatism.
• Axis describes the positioning of the cylindrical power on your lenses (required for astigmatism).
  <Note: you will not be able to use a contact lens prescription – the two are different.>

2. Measure Your Pupillary Distance

Pupillary Distance (PD) is the distance between your pupils – usually measured in millimeters.

The optical centre of the lenses gives you the truest vision. This part of the eyeglasses should be directly in front of your pupils.

To get the correct positioning of the lenses on your eyeglasses, the eyeglasses lab needs your PD. Pupillary distance generally falls between 54 and 68 mm. It can be tricky to measure your own PD. It is best to have it measured by a skilled optician.

Optometrists will note this measurement during your eye examination but may omit the PD from your prescription because it gives consumers the ability to shop online. Ask them to write this number in your prescription, if they haven’t already.