Eyeglass Lens Styles
Single Vision lenses are lenses that have the same prescription all the way through. They are generally designed for people under the age of 40 that need help seeing either things at a distance, or things up close (People who are nearsighted, farsighted, or just need reading or computer glasses).
An older lens design, lined bifocals generally have a small, "D"- shaped segment in the bottom portion of the lens that contains the patients reading or computer prescription (Dr. Cochrane can custom-tailor this distance to your specific needs). They are nice because it is very defined where the distance prescription ends and the reading prescription begins, although, unless you select the 3-section trifocal design (as opposed to the 2-section bifocal design), you do not have a clear intermediate / computer / arms-length section to the lens. Many patients also find that the sudden "jump" that happens between the distance and reading portions of the lens- and the line itself- to be distracting when compared to the gradual changes offered by a Progressive lens.
Lined bifocal lenses can be put into smaller frames than lined trifocal or progressive lenses.
Lined trifocals, as opposed to bifocals, have three "segments" or viewing areas, rather than two. The top part of the lens is designed to see distance, then there is a section of mid-range / computer / fingertip-distance, and then there is a reading section at the bottom. Trifocals require a decently deep / tall frame in order to give you a comfortable amount of each part of the prescription.
Progressive / "No-Line" Bifocal
Progressive lenses are much more natural feeling than lined bifocal or trifocal lenses. Inside a progressive lens, the prescription gradually "fades" from the distance prescription at the top to an intermediate / computer distance, to a reading distance.
In order to allow the lens to have a clear progressive "corridor" of crisp vision down the center of the lens, the optics of the peripheral portion of the lens (mostly in the bottom half or so) are compromised. Most people easily adapt to this, however, and consider it a worthwhile trade in exchange for not having a very obvious line or two running across the bottom of the lens.
There are many different styles of progressive lenses available. "Standard" progressives offer an average "corridor width." You might find that you have to turn your head a bit to read across an entire newspaper page or other wide surface.
Newer "Digital / Wide Corridor" progressives offer several distinct advantages over Standard progressives. Obviously, they have a wider corridor, so you don't get as much "swim" or "fishbowl-effect" as you glance out of the sides of the lenses. Also, the transition between the distance - computer - reading zones is much smoother and more comfortable. Finally, some of the newest designs of these Wide Corridor lenses offer a fourth "zone" designed for smartphone and tablet use.
Many progressive wearers notice that, while their Standard progressives function fairly well at a traditional reading (close to the body and closer to the face) and computer zones, they struggle a bit when they try to check their phone or read their Kindle. Most tablet / e-reader / smartphone users tend to hold their phones a bit higher and farther away than they would hold a book, yet not as high or far away as their computer monitor. This fourth zone brings your technology into clear focus without a lot of inconvenient up-and-down head movement.
There are times when none of the above mentioned lenses will solve all your visual needs. People in certain occupations have unique needs that only an occupational lens will solve.
The most common occupational lens is called a "Double-D" or "Occupational Seg." This lens looks like a traditional lined bifocal, with the addition of an extra reading segment at the top of the lens. It is useful for people that do close work above their heads, like electricians.
We can also do a modified version of a "Double-D" lens by just flipping a traditional bifocal lens upside-down, so that the reading is in the top and the middle and bottom of the lens are distance only. This would be a good solution for someone who needs help seeing close things above them, but still needs to be able to look down and easily see their feet.
Many times a customized prescription can be written for a patient with specific optical needs. This, rather than an exotic occupational-style bifocal, can usually help solve any major vision issues an individual may be experiencing. Dr. Cochrane is happy to discuss your exact situation and write you a custom prescription individually tailored for your specific uses.