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Lens Styles

by | Feb 25, 2018 |

You and your optician spent some time finding that perfect frame that reflects your personality, your lifestyle, your image.  That is what everyone else sees.  Now it’s time to get to the most important part of your eyewear…and that is what YOU see.  A lot of the lens “style” is predetermined by your prescription requirements.  Here we will discuss the main styles and what they offer.

Single Vision Lenses

S ingle Vision Lens have one corrective power across the entire surface of the lens.  It is use to correct one vision condition such as myopia (nearsightedness) or hyperopia (farsightedness)  with or without correcting astigmatism (distorted vision as a result of irregularly shaped lens or cornea).

As a result, a person who has been corrected for far distance must accommodate to see clearly up close.  If they can not accommodate then they either need a separate pair for near vision or a multifocal lens design.  A person who has been corrected for near distance must accommodate to see clearly far away.

Single vision correction may be the first step into vision correction for most people and it has often been seen as nothing more than a slight “inconvenience” for the wearer.  Once the wearer gets their correction they may have “20/20” vision but still feel as though it could be better.  This may be attributed to higher-order aberrations often associated with the limitations of conventional manufacturing of spectacle lenses.  Those aberrations are more pronounced in stronger prescriptions or more complex progressive designs but along comes digital free-form high-definition single vision lenses and the world has changed!

Take a minute and read about “Digital Free-Form” to better understand where this is going.

Recent advances in manufacturing technology has made it possible for the single vision wearer to have the sharpest vision than ever before.  The extreme precision of high-definition free-form single vision lenses produces lenses 100 times more accurate than conventional manufacturing.  This is the first time it has become possible to optimize compound prescriptions in the peripheral area making distortion a thing of the past.  Lens performance can be further advanced by accounting for pantoscopic tilt, frame wrap, vertex distance, frame size, frame shape and pupil height.

At the time of this article Zeiss has taken this technology a step further.  Now offering the Zeiss EnergizMe designed specifically for contact lens wearers this lens features Digital Inside Technology with Zeiss Duravision BlueProtect.  Ask our optician if the new Zeiss EnergizeMe Lens is right for you.

Bifocal Lenses

B ifocals are lenses with two distinct corrective powers.  Bifocals are commonly prescribed to presbyopes who require a correction for myopia (nearsightedness) or hyperopia (farsightedness) with or without correction for astigmatism (distorted vision as a result of irregularly shaped lens or cornea.  The primary purpose of a bifocal lens is to provide the optimal focus balance between distance and near vision.  Generally, you look up and through the distance portion of the lens when focusing on points farther away, and you look down and through the bifocal segment of the lens when focusing on reading material or objects within 18 inches of your eyes

It is generally accepted that Benjamin Franklin invented the bifocal.  The most common bifocal today is the Straight Top 28 Bifocal which has a straight line across the top with a 28mm radius.  There are several varieties of straight top bifocals available today including: Straight Top 25, Straight Top 35, Straight Top 45 and the Executive (The original Franklin Seg) which runs the complete width of the lens.  In addition to straight top bifocals there are completely round bifocals including Round 22, Round 24, Round 25 and Blended Round 28 (no definitive segment).  The advantage to the round segment is that there is less image jump as one transitions from the distance to the near portion of the lens.

OCCUPATIONAL BIFOCALS

Occupational bifocal lenses are designed for performing a particular job or hobby and are not meant for general-purpose wear.  One popular occupational bifocal lens is the “Double-D.” This lens has an upside-down flat-top segment for near or intermediate vision in the top third of the lens and a second flat-top segment for near vision in the bottom third.  The segments are commonly offered in 28mm and 35mm varieties.  The Double-D occupational lens is great for car mechanics, who need to see their tools and other near objects, but also need to work on vehicles on a lift above them.  The upper segment helps them see the undercarriage of the vehicle without having to tilt their head far backward.

Trifocal Lenses

T rifocals are lenses with three distinct corrective powers.  Trifocals correct for distance, intermediate (arm’s length) and near vision.  Trifocals are commonly prescribed to advanced presbyopes who require a correction for 2 diopters or more of reading addition.  The intermediate portion of the trifocal lens is typically half of the addition power.  Therefore, a person with a -5.00 diopter distance power with a +3.00 add power would have net reading power of -2.00 diopters and an intermediate power of -3.50 diopters.

The most common trifocal today is the 7x28 trifocal which has a straight line across the top with another straight line 7mm below that (this is the intermediate portion of the addition) and a 28mm radius .  There are several varieties of  straight top trifocals available today including: 7x25, 7x28, 8x35, and the Executive Trifocal which runs the complete width of the lens.

There are specialty trifocals available that are often suggested for those who spend a great deal of time on the computer and for those 50 years an older who are having a harder time accommodating.  As mentioned above the standard intermediate power for the trifocal is 50% of the total add power.  This line of trifocals (called Acclaim 61) has an intermediate power that is 61% of the total add power.  These trifocals come in 8x34, 10x35, 12x35 and 14x35.  Material options for lined trifocals is more limited than with other lens designs.

Some people are reluctant to try trifocals because they are concerned about the appearance of the lenses or are worried that trifocals will be difficult to get used to, since the top line of the intermediate zone is close to the center of the lens. But in fact, most people who try them are very pleased with the added range of vision trifocals provide (compared with bifocals) and the wide field of view they offer for computer use.

Progressive Lenses

P rogressive lenses are lenses with three distinct corrective powers.  Progressive lenses correct for distance, intermediate (arm’s length) and near vision.   The primary difference between a progressive (no-line) lens and traditional straight top trifocal is the blended or gradual progression between the three viewing zones.  Cosmetically preferred over the traditional “lined” trifocal, no-line lenses have a history dating back to the early 1900’s.  It wasn’t until the 1970’s that progressive lenses established a consumer following.

Progressive lenses are commonly prescribed to advanced presbyopes who require a correction for 2 diopters or more of reading addition.  The intermediate portion of the progressive lens is typically half of the addition power.  Therefore, a person with a -5.00 diopter distance power with a +3.00 add power would have net reading power of -2.00 diopters and an intermediate power of -3.50 diopters.

Please take a moment to read the article on “Digital Free-Form” lens manufacturing to learn the benefits of a truly custom made pair of High-Definition lenses designed exclusively for you, your prescription, the frame you choose, the way your wear that frame and your daily lifestyle.  Your world will never look the same.  Stop by the store today to learn more.

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