Merchant Processing Services

Blinded by the Light

To understand how polarization works, one must first understand how light works and effects the eye. There are three different forms of light: ambient light, direct light, and reflected light.

• Ambient light- Ambient light is diffused lighting that has no visible direct source. This light has been bounced and scattered around so much that it just seems to glow. Good examples of this are the soft light that is visible at night or the scattered lighting that is used in photography to create effects. This light type is not a major source of discomfort.
  

• Direct light- Direct light is light that goes straight from the source directly to the eye. In this case, it would be sunlight. Bright sunlight can cause pain during focusing and it can wash out the colors and fine details of the surrounding environment. 
  

• Reflected light- Reflected light, as the name implies, is light that is reflected off a surface before it enters the eye. This is the light that becomes horizontally polarized during the reflection process, resulting in glare.

Reflected light and its resultant glare is a major cause for concern to the eye care professional and his or her patient. Glare and the dangers it causes can be divided into two main categories: discomfort glare and disability glare. 

Discomfort glare is a very subtle form of glare. It causes the visual system to over exert itself resulting in eye strain, headaches, and physical fatigue. Common causes of this glare type are light that is reflected off spectacle lenses, computer screens, windshields; as well as light color surfaces such as paper and walls. 

The most dangerous form of glare is disability glare. This is the type of glare that causes the patient to instinctively avert his or her eyes. Reflection off the roads, water, ice, hoods of vehicles and sand are the main causes of this glare type. Further, it is disability glare that most concerns the eye care professional when providing the patient with the appropriate sunwear. Disability glare poses a hazard to the patient if not treated properly, due to safety risks that averting the eye can cause during activities such as driving and water sports.

Regular windshield glare

Glare reduced with Nupolar® from Younger Optics

Changing the Ray

Polarization is the breaking down of a light wave that travels in all directions, into rays that travel in two directions. Although the direct light coming from the sun in not polarized, when the light hits a highly reflective surface, it is broken down into horizontal and vertical polarized beams. Since most reflective surfaces are on a horizontal plane, such as water or the hood of a car, the polarized beams that cause the most disability glare is the horizontal polarized light. Therefore, to eliminate the horizontal polarized light from reaching the eye, a filter is fixed at an angle that only allows vertical polarized light to enter the eye.

It’s all in the Film

A standard sunglass lens is simply tinted or coated and is insufficient in blocking or reducing the amount of glare. These lenses simply reduce all the visible amount of light that enters the eye by a standard amount, based on the degree of color on the lens. This is not the case with polarized lenses, which are actually an optical filter. 

Polarized lenses are composed of a chemical film that is applied to a clear lens surface. The chemicals within the film, usually iodine crystals, typically align themselves parallel to each other, creating a window blind effect that blocks wavelengths on one plane while allowing wavelengths on a plane 90 degrees away to pass through the lens. 

The common methods of creating polarized lenses are lamination, during a molding process, or by coating a lens. Lamination is the oldest form of polarization and is created by placing a polarized film between two pieces of lens material. Although not considered a significant problem today with new manufacturing methods - delamination, or the separation of the polarizing film from the lens material, used to be a major concern for eye care professionals. 

The polarization of plastic lenses occurs when the lens material is melted and then poured into a mold in which film is placed. Next, the lens material surrounds the film, hardens, and creates one solid piece. With polycarbonate lenses, the polarized film is placed on the outside of the lens and is then covered with a scratch resistant coating. This method is used because the heat from the injection molding process of polycarbonate manufacturing will degrade the polarizing film.

Customizing the Lens

In determining which polarized lens to provide to the patient, it is important to understand the patient’s needs and desires. The new lines of polarized lenses can be customized by material, design, and color.

Early polarized lenses, like most lenses, were only available in glass and consequently a safety concern. This is no longer the case. Today’s polarized lenses are available in plastic, hi-index and polycarbonate, in addition to glass. Therefore, they are an excellent choice for even the most active patient. 

No longer do polarized lenses come in the standard single vision design. The wide varieties of lens designs now include aspherics, progressives, bifocals and trifocals. These new designs allow the eye care professional to make the lenses customizable for many tasks and prescriptions. Now, a high minus presbyope can get a lens that works well for golf, as well as driving. In fact, virtually any activity that will benefit from color enhancement, increased depth perception, greater color contrast, and the elimination of glare will be improved with the addition of polarized lenses. 

Polarization is now available in a wide range of colors. No longer does the patient have to be content with brown or gray. Now, the eye care provider and patient can design the polarized lens to have a color that is best for the desired activity. New colors such as copper for racing, green for tennis, and orange for hunting and shooting are now available to enhance performance. 

Words of Advice

Although the benefits of polarization are excellent for almost all patients and outdoor activities, some visual activities may be hampered by polarization. Pilots who operate aircraft with polycarbonate or tempered-glass windshields may be distracted by the stressed, checkerboard pattern that may appear in the material. Activities that may require use of a LCD screen may also be hampered by polarized lenses since LCD screens operate by polarizing light. An additional activity that may pose a danger to individuals wearing polarized lenses is downhill skiing. Glare for high speed skiers is a safety asset due to its ability to alert skiers to ice patches and bumps on a ski slope.

Polarized lenses are the best lenses available for sunwear and most outdoor activities. By actually filtering the light instead of just diminishing it, polarized lenses create a safer, more comfortable environment for the patient by eliminating glare and also by reducing eyestrain, headaches and fatigue. It is the responsibility of the eye care professional to provide the best possible eyewear to fit the patient’s needs and polarized lenses provide an unsurpassed means to do this.

Carrie Wilson
BS, LDO, ABOAC, NCLEC