Here we present the "spectacular" options and choices for lenses materials, frames selections, tints etc.
Spectacle Lens MaterialsThe 3 most common materials used today are glass, plastic, and polycarbonate. Glass and plastic are no different in cost, or optical quality, however plastic scratches easier and is only half the weight of glass. The third type, polycarbonate, is used for safety Rx's and sports eye wear. It is an extremely high impact plastic, but is also subject to scratches.
High Index Lens Materials
These materials are thinner for the same lens power. People with high Rx's will benefit from this lens type. In general, the higher the index, the thinner the lens edge, but the more the internal distortion and chromatic abberation. This type of lens is only worthwhile for high to moderate Rx's. Polycarbonate lenses can be made thinner without the risk of breakage, and this is another way to reduce edge thickness.
This is another way to reduce lens thickness, especially for farsighted patients. These lenses require precise centering in front of the eye, but will reduce thickness and weight by about a third.
This type of coating reduces the internal reflections inherent in all spectacle lenses. Normally, about 92% of incident light will pass through a lens, but the other 8 % makes glare and internal reflections, especially in the dark. With the AR coat, about 99% of the light passes through. This not only reduces glare, but people looking at you will see less of your lenses annd more of your eyes. The drawback here is that a more transparent lens is tougher to keep clean - any smudge or fingerprint shows up better, so special cleaners are necessary.These coatings are standard with high-index lenses.
Tints do the opposite of AR coats - they reduce lens transparency. Tints are more effective in reducing glare in bright situations, such as in the office environment and for computer operators. Tints can also be applied for cosmetic reasons.
Lenses that darken as you go outside are available in glass or plastic. It is the UV light in sunlight that triggers the change - normally these will darken in 1-2 minutes but take 4-5 minutes to lighten up again indoors. If you are sitting in a car with the windows rolled up, less UV light is available to change the lenses, and they might not get as dark, or take longer to change compared to full sunlight. Colder temperatures allow more darkening to occur. These are 100% UV rated.
This is the standard type of bifocal, with the small half-moon or round shapes in the lower half of the lenses. These are relatively inexpensive, and allow a wide horizontal field of view, and come in various widths. In general, the wider the bifocal segment, the wider the field of view for reading, and are good for people doing a lot of desk work, but this does tend to take awayy some of your peripheral vision while walking around. Standard width is 25mm, but these are available in 28, 35, 45mm as well as all the way across your lenses.
No-line Bifocals or Progressive Multifocals
These lenses are a gradual transition between top and bottom powers, and some first time bifocal wearers find them easier to adapt to, but they are more expensive. Theey were originally designed for cosmetic reasons. In the transition zones around the lens periphery, you get distortions. This leads to an effectively reduced horizontal field of view in the reading zone, and your reading material must be within a foot or so of center when using these lenses.
This type of lens has an extra set of lines in the lower portion. This intermediate add allows the wearer to see in the intermediate distance i.e. at arm's length. Unless you are always working at that distance, the extra lines might cause more trouble than they're worth, but these can be indispensible for computer users over age 50.
Sun Glass Options