Lenses — An Overview
(Single Vision, Progressive, Computer Lenses, Bifocals, Trifocals, Links)

In the past, if you wore eyeglasses, your lens type options were limited.  Now, lenses are available for all kinds of visual impairments.  Depending on your age and visual needs, you might be given a prescription for either single vision or multifocal lenses.

Single Vision Lenses

• Single vision lenses have the same lens prescription throughout the entire lens. Nearly all prescriptions written for children and young adults are for single vision lenses.

•  Single vision lenses may be prescribed for full-time wear or only for certain activities such as driving, reading or computer use.

Multifocal Lenses

When we reach our mid-forties, many of us need a little help reading small print.  Multifocal lenses are prescribed to correct this normal age-related change called presbyopia (arm's too short syndrome!).  Multifocal lenses have one lens prescription for distance vision and one or more additional prescriptions in the lower part of the lens for near vision.  Multifocal lens types now include progressives, computer lenses, bifocals and trifocals.

Progressive Lenses   Video

About 50 percent of eyeglass wearers in the U.S. who need multifocals wear progressive lenses.  Progressive lenses are more expensive than the other multifocal alternatives, and not all vision care benefit plans cover this lens option.

• Progressive lenses have one prescription in the upper part of the lens for distance vision and a progression of several additional prescriptions in the lower half of the lens for viewing objects at intermediate and near distances.

• Because there are no abrupt changes between lens prescriptions, progressive lenses have no visible lines.

• Progressive lenses provide clear, uninterrupted vision at all distances.

Computer Lenses   (video)

• Are your eyes tired? Is your neck aching? Your bifocals weren't designed for the Web.

  When you look at the computer screen how well do you see?

  No wonder your eyes get so tired! If you wear bifocals, your prescription allocates the lower segment of your lens for close work and the upper segment for far distance vision.  But when you are working at a computer, the critical area for vision is all within a 3-foot radius, therefore you are only utilizing half of your glasses.  As a result, you must continually move your head up and down to focus on your work space.

  No-line Progressives narrow your field of vision, just where you need it most.

  No wonder your neck aches!  Progressive lenses remove the annoying, unattractive bifocal line, but they also narrow your field of vision — right in the middle of your computer screen where you need it most.  The focus isn't the best for computer use and you have to move your head from side to side to see it all clearly.

  Ordinary bifocals put a line between you and what you see on the screen.

  No wonder you get so tired!  Bifocals are designed only for distance and close-up work. There's no clear midrange vision.  With bifocals you can see only your keyboard and things in the far distance clearly.  To keep your screen in focus you must tilt your head back and forward.  And the line is always in view.

  See freely.  Work comfortably.  Computer lenses give you an improved view of your screen.

  With Computer Lenses™ you can see everything within your computer workspace clearly — out to a distance of about 7 feet*.  And your best, clearest, biggest focus area is right where you need it to be, on your computer screen. You can sit and work comfortably and see your best without strain.  Computer Lenses are not for use away from your desk but they make the hours you spend with your computer more effective, easier and less of a strain on your eyes.

Bifocals

Bifocals still account for about 40 percent of multifocal lenses sold in the U.S.  While they might provide a less satisfying visual experience than progressive lenses, bifocals are an acceptable choice for long-term wearers who are satisfied with their vision or who have budget constraints that preclude purchasing higher priced progressive lenses.

• Bifocals have one lens prescription in the upper part of the lens for distance vision and one prescription in the lower portion of the lens for reading and other near tasks.
• The boundary between the two prescriptions is distinct, creating a visible "bifocal line."
• Because they have only two lens prescriptions, objects at intermediate distances (e.g. your computer screen, items on a grocery shelf, etc.) may appear blurred with bifocals.

Trifocals

Trifocals account for only about 10 percent of multifocal lenses sold in the US. These are primarily occupational lenses for wearers who feel they need a larger intermediate and near zone in their multifocal lenses than that provided by progressive lenses. Trifocals typically cost more than bifocals, but less than progressives.

• Trifocals have one lens prescription in the upper part of the lens for distance vision, a second prescription in the lower portion of the lens for reading and a third prescription between the two for viewing objects at intermediate distances.
• The boundaries between the three prescriptions in trifocals are distinct, forming two visible lines.
• Trifocal wearers may experience the same image jump sensation as bifocal wearers.

Links:   Hoya Optical
            Optima
            SOLA Optical
            Zeiss Optical
            Opticians Course: Optics of Light
            Opticians Course: Ophthalmic Lenses

100 North Rancho Road, Suite #1
Thousand Oaks, CA   91362
Phone (805)495-3937   Fax (805)373-9843
E-Mail

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