Each lens material has its own unique optical properties. Depending on prescription and intended use, certain materials perform better than others.

Aspheric lenses provide superior peripheral vision for those with stronger prescriptions and also produce thinner edges than spherical lenses.

Highly impact resistant materials such as polycarbonate and Trivex are required for children’s lenses as well as for all sport and other safety applications.

Lens edge thickness depends on prescription, frame size and shape, center thickness and on the index of refraction of the material. Currently, there are eight possible choices of index of refraction ranging from 1.49 to 1.74. As this number increases, lenses become thinner for a given prescription in a given frame. Some of the manufacturers that make higher index, thin lenses are: Seiko; Essilor; Hoya; Nikon and Optima.

Ultraviolet (UV) protection is recommended for all lenses that are used outdoors and for use with computer monitors.

Harmful blue light (HEV) protection is recommended for all lenses used to view digital screens on computers, cell phones and other devices.

Sun lenses, whether prescription or non-prescription, must filter out at least eighty to ninety percent of visible light and must filter out all ultraviolet (UV) light. Polarized lenses offer the additional feature of blocking light reflected from horizontal surfaces and are a must for all water activities.

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Transitions Lenses darken only with direct exposure to sunlight and do not work effectively behind the windshield of a vehicle.

Fashion tints can be selected for appearance or to soften light in certain lighting conditions. They do not meet the standards required for sun wear.

Scratch resistant coatings are necessary and should not be considered an option. Extra hard coatings such as Essilor’s TD2 offer enhanced scratch resistance.

Anti-reflective treatments increase light transmission, reduce glare and reflections and greatly improve the appearance of lenses. The very thinnest lenses require this treatment, while it is optional on the others. Basic, low-end treatments perform poorly. The best anti-reflective treatments combine superior scratch resistance with hydrophobic and anti-static properties, and are chemically bonded to the lens.  Some key brands are: Crizal Avance; Crizal Alize; Crizal Prevencia; Hoya’s Super High Vision and Seiko’s Super Surpass ECP.

Bifocal and trifocal lenses are made in many widths and depths to accommodate a variety of needs. Blended bifocal lenses are also available, but are generally not recommended.

Specialty, occupational multifocal lenses can help with tasks that require intermediate or near vision in areas above eye level.

There are over two hundred progressive lens designs made by numerous manufacturers. Early designs caused distorted vision for some wearers. Some of the low-end lenses on the market today still cause this problem. Today’s premium lenses are more costly, but provide far superior visual performance. These modern progressive lenses include designs that maximize distance, intermediate, or near visual acuity. Lens choices include many that have been created to work well with today’s shallower frames. Some current premium progressive lens-makers include Essilor’s Varilux, Hoya, Shamir, Seiko and Zeiss. Newer, digitally manufactured progressive lenses customized for the individual wearer produce the very best visual results.

Computer lenses perform best with anti-reflective treatments combined with UV and HEV blue filters. Light tints can also help to further reduce glare. Special progressive and bifocal designs that maximize intermediate and near vision are offered for those who can no longer focus well at these distances.