Progress in Progressives

New styles and technological breakthroughs are providing more than just a "no-line" alternative to bifocals and trifocals.

By Brian P. Dunleavy

These days, you have a lot to choose from when it comes to progressives - lenses specifically made for those with presbyopia that correct vision at every distance, eliminating the need for several pairs of eyeglasses.

Besides being a handsomer "no-line" alternative to traditional bifocals and trifocals, progressive lenses are now custom-made to fit every lifestyle need - from daily wear to occupational, from fashionable to leisure.

In the past, some dispensers hesitated to prescribe progressives because of inherent design problems, including distortion in the periphery, narrow intermediate corridor and a narrow-reading area. These issues caused many potential progressive wearers to become "non-adapts," suffering from headaches and even dizziness when converting from bifocals to progressives or when starting with progressives.

But designs have changed substantially and new "generations" now allow for a smoother transition between segments. They also offer a wider near-vision segment that allows for easier reading and "close work" for progressive wearers.

As an extension of these improvements, experts say, distortion has been significantly reduced in most of the progressive designs newly introduced to the market. The result of all these changes is better overall vision, improved peripheral vision and reduced incidences of headaches or dizziness when looking through the lens. In other words, fewer non-adapts.

"Patients we've placed in [new generation] progressives are happy with the lens performance," explains Anthony Webb, OD, who runs an independent optometric practice and dispensary in San Antonio, Texas. "They are much more comfortable because of reduced distortion. We're getting much more positive responses with the new designs."

"Short-Corridors" Change a Big Problem

One of the biggest improvements in new designs, Dr. Webb says, has resulted in the ability to fit them into smaller frame styles, which are among the more popular styles.

This technology has actually resulted in the rise of a new sub-category- "short-corridor" progressives. In order to provide an adequate viewing area for distance and near vision, the finished progressive lens (and therefore the frame) needs to be of a minimum fitting height. In the past, that number hovered around 23-25 mm, virtually eliminating the smaller frame sizes popular today. Short-corridor progressives, however, compress the little-used intermediate area of the lens (hence the name), allowing for smaller frames.

"I'm selling a lot of smaller frame sizes so I'm using a lot of the short-corridor lenses," notes Carter Lowry, optician and owner of New Opticians in Lexington, Va., adding that short-corridors account for roughly 20 percent of the progressives he sells. "I very seldom need to rule out frames now."

Experts say the visual sacrifice of short-corridor lenses is minor because most patients use progressives for near (e.g., reading) and distance (e.g., driving) tasks anyway. The minimum height, however, still depends on the lens design and the patient's visual needs. "Younger patients do well with them because their eyes can transition from the distance to the add very quickly," says Lowry. "But older patients and long-time progressive wearers like that intermediate zone because they need the transition. All patients lose more intermediate zone as their bifocal add goes up."

Preventing Computer Vision Syndrome

Speaking of intermediate vision, manufacturers have also developed a new category of no-line bifocals offering enhanced near and intermediate vision (out to 10 feet) specifically made for computer users. Several lens manufacturers now offer products that fit into this emerging category, which are believed to be a solution to computer vision syndrome (CVS), the eyestrain or fatigue computer users often feel after extensive time behind the keyboard.

Although standard progressives have become the state-of-the-art lens for patients needing both distance and near powers (i.e., presbyopes), they do not have an adequate near vision segment for computer users, while reading glasses do not allow for sufficient distance vision (with acuity ceasing approximately 18 inches from the patient's face).

Jeff Anshel, OD, owner of Poinsettia Vision Center in Carlsbad, Calif., who lectures nationally on the topic of computer vision, recalls a phone call he received from the Monterrey aquarium in California. The aquarium's employees, it seems, were having difficulty with computer eyestrain. When Dr. Anshel visited the facility, he found that most of the workers were wearing standard progressives.

Both presbyopic and single-vision plus and minus patients have benefited from the use of "computer lens" products in occupational settings. In addition to computer users, other occupations that may benefit from them include architectural drawing and drafting, writing and any artistic endeavor such as painting and sculpting.

Dr. Anshel says that more and more practitioners have added computer/occupational vision as a sub-specialty to their practices. To determine whether these products will work well for particular patients, he says, requires special attention to the patient's workplace environment and the activities of their occupation. Each lens design also has its own, unique fitting requirements.

Computer vision lenses are only the first in what may become a variety of "task-specific" lenses in the progressive category. "Task specific lenses are the future," notes Dr. Anshel. "As an industry, the challenge now is to differentiate what's out there and when these lenses should be used. Patients can't benefit from these products unless we as professionals dispense them correctly."

Posted: Oct. 29, 2001