Photochromic is a generic term to define a lens with a characteristic of changing state from clear to sunglass dark when exposed to light.

Videos of missile drop tests perfomed by Younger Optics on CR-39, 1.60, Polycarbonate, Spectalite, and Trivex (Trilogy).

Y-Stick assists the optician, using the traditional manual method of marking the fitting crosses. The measurement is consistent; as long as the customer assumes the same body posture, the measurement will be the same. Any subjectivity on the part of the optician has been removed.

Introduction to the many different styles of lenses available including single vision, progressives, occupational, and more

Even though Trivex has been available for a while now, there is still much debate and confusion about how Trivex and polycarbonate stack up against one another. We'll lay out the facts and attempt to put the question to rest.

A progressive addition lens (PAL) is a type of multifocal lens that employs a surface with a continuously smooth increase in addition (Plus) power. The curvature of the surface increases from its minimum value in the distance zone to its maximum value in the near zone (Figure 1). The total increase in surface power between these two zones is equal to the specified Add power of the lens. This gradual increase in power also results in a variable focus intermediate zone.

Frequently, a presbyopic patient may come in having had their prescription filled elsewhere, requiring new or replacement progressive lenses. In these situations it may be helpful or even necessary to identify what kind of progressive lens the patient is currently wearing.

The first time you recommend bifocals, you can almost hear what they are thinking "Oh my, now I am getting old!" The cosmetic issues associated with bifocals or trifocals are more profound than any other spectacle aesthetics issue.

Aspheric design lenses combine multiple curves in their front surface which allow for improved off-center optical performance without large increases in thickness. Aside from the improved optical characteristics, this greatly enhances the cosmetics of the spectacles in a variety of ways.

The principal use of aspheric lens designs is the reduction or elimination of optical aberrations produced by looking through an ophthalmic lens obliquely.

All optical materials, no matter how advanced or well-suited for a patient's needs, suffer from innate shortcomings specific to the lenses chemical makeup. There are many different types of coatings available to help make up for these shortcomings.

AR coating can minimize lens surface reflections, significantly reducing or eliminating the problems discussed above, reducing eye strain, while allowing more light to reach the eye, improving contrast and clarity.

Photographers often use polarized lenses on their cameras to obtain bolder colors and deeper contrast in their photos. In the same way polarized lenses remove the glare and improve the visual quality of a photograph, polarized ophthalmic lenses improve the vision and comfort of those wearing them, in addition to playing an important safety role for drivers, particularly in morning and late afternoon sun.

Polarized color availability, efficiency, transmission, and common usage

It is an all too common misconception that yellow tinted or yellow polarized night driving glasses are beneficial for night time driving.

Have you ever had the chance and check a pair of lenses that were treated with a UV solution some three to six month after the were made and handed to the patient? There is a good chance, that you will have a big surprise, your UV Meter ( if the instrument measures at 400 NM) will read no UV absorption or one that is way below an acceptable standard. Lets try to analyze this fact.

Harry A. Saake's 101 (Okay, 44) Tips for Dispensing Opticians