STRATEGIC SKILL BUILDERS: Continuing Education
TORIC LENS TECHNOLOGY
A Look at Today's Torics
How far we've come technologically since the 1980s.
Walter D. West, O.D., F.A.A.O., Brentwood, Tenn.

Toric soft contact lenses began finding their way into eyecare practices in the late 1970s. Since then, the quest for the perfect toric soft contact lens that works every time, on every patient, has continued.

We embrace new designs, materials and modalities as manufacturers make them available, and in doing so increase our success rates in fitting more patients. Here, I'll give you a history of this modality and explain what you need to know about fitting torics successfully.

THE HURDLES WE FACED

From the beginning, lens manufacturers and doctors alike realized that the primary focus in toric lens design was rotational stability.

Early designs utilized prism ballast, while later designs combined prism ballast with truncation. Some enterprising doctors even attempted to truncate prism-ballast designs in their offices by dehydrating the lens and truncating the inferior edge with everything from razor blades to emery boards to diamond rigid lens modification tools.

These attempts at "in-office" modification were generally unsuccessful but demonstrated the willingness of the doctors to try almost anything they could think of in order to stabilize toric soft lenses rotationally.

Of course, the early toric soft lenses that employed truncation as a method of stabilization generally got better rotational stability -- at the expense of patient comfort. In addition, truncated lenses were plagued with coatings of meibomian secretions, denatured lysozyme and other tear components.

We continue to face this problem today. Any lens design that stabilizes rotation exposes the horizontal meridian of the lens to a greater degree of coating, though not to the same degree as with a truncated contact lens.

Because of its constant position rotationally and the lack of lid movement over the entire surface, toric soft lens coatings aren't blinked away, as they are with a spherical soft contact lens that's allowed to rotate slightly with each blink of the patient's eye.

Another concern with prism-ballasted designs, even now, is the lower amount of oxygen that's conveyed to the inferior portion of the cornea through the relatively thick portion of the lens.

Attempts to reduce concerns for oxygen transfer through the generally thicker, prism-ballasted soft toric designs included using lens materials of higher water content to effectively improve Dk/L and ultimately increase the amount of oxygen to the cornea.

However, many of the Type 4 ionic materials had problems with lens coating.

REPEATABILITY AND CONSISTENCY

Our difficulty in successfully fitting patients with toric lenses -- and their difficulty in wearing them -- is mainly a function of lens design and materials and of the repeatability and consistency with which lenses are produced. Just as there are more variables for us to consider in fitting these lenses, there are more variables for manufacturers to confront in production.

Lathe cutting and then polishing was once the only means of manufacturing toric soft contact lenses. The performance of all soft toric lens designs suffered from inconsistent manufacturing and from the manufacturers' inability to accurately assess the lenses they distributed.

Once an astigmatic patient was fitted with trial lenses and the rotation of the lenses was noted and compensated for in the final design, doctors expected all subsequent lenses they ordered for the patient to perform in the same manner.

Unfortunately, it didn't always work that way. Some of the variables that frustrated eyecare professionals and manufacturers alike included:

• variability in the amounts of prism ballast

• the position of the ballast

• differentials in thickness

• inaccurate powers (both sphere as well as cylinder)

• misalignment of the optical centers of the front and back surfaces.

These rogue variables, coupled with inability to "verify" the lens parameters, often resulted in doctor frustration and patient failure.

Unfortunately, doctors who weren't up to the challenge of an inexact new technology threw in the towel and began telling patients, "If you have an astigmatism, you can't wear soft contact lenses." Today, we suffer the consequences of this inaccurate mindset.

Many astigmatic patients still believe they can't wear contact lenses. Luckily, however, other doctors saw the potential of these lenses and recommended them to their patients. Fitting them became more successful and more profitable.

Although many of us paid for our soft toric clinical education in the form of non-returnable extra lenses that filled our cabinets, very few would trade anything for the experience and the insights gained through this process.

ARE WE SURE WE'RE DOING THIS RIGHT?

In the 1980s, greater interest in toric fitting led to the realization that success rates could be improved by merely tightening the tolerances in manufacturing and developing better systems for monitoring the manufacturing process.

One such system was Statistical Process Control, in which the toric lens was evaluated for accuracy during every phase of the manufacturing process, rather than only at the end of it. Another innovation was labeling the lenses with the powers and axes that they actually were, rather than what they were supposed to be.

The contact lens manufacturers recognized two characteristics about the toric soft contact lens market, starting the race for accuracy and performance that we continue to see today:

1. They recognized the potential profit for a virtually untapped portion of the eye care market.
   At the same time, they realized that eyecare professionals wanted to increase their earnings and that they'd be loyal to a soft toric product that performed consistently and profitably.

2. They recognized that, in part, they needed to take responsibility for the success and satisfaction of the patients. As a result, they began to sponsor one of the broadest continuing education efforts in the history of the industry. Continuing education classes on toric soft contact lenses became commonplace at national, regional, state and local society meetings across the nation.
   In addition to their effort to train eyecare professionals in fitting soft toric lenses, manufacturers began to offer attractive trial lens opportunities as well as lens exchange privileges, performance warranties and "no fault" guarantees. With these advantages, eyecare practitioners began to embrace soft toric lenses in greater numbers and with greater success than ever before.

ANOTHER MOUSE TRAP

As in any immature market, someone always questions why things are being done the way they are. So it was with the prism-ballast design. Some industry members thought that the use of a "double slab-off "or "thin zone" design could enhance lens comfort and stability. They set out to prove it.

In the 1980s, two such lens designs came onto the market in a conventional lens modality. Another appeared in 2000, in a disposable modality (more about that later). Again, eyecare professionals embraced these new designs and were successful with them.

Doctors began to realize, however, that no single lens design, material or manufacturer could ever suit every patient. Yet manufacturers kept trying to create a lens that would do just that. This focus accounts for the many advances in lens predictability and performance that we now enjoy. The opportunity to choose from low or high water content, front or back surface toric, prism ballast or double slab-off, ionic or non-ionic are all the result of someone's effort to improve toric soft lenses.

REVOLUTION!

Beginning in the late 1980s, a new manufacturing process -- molding -- revolutionized the contact lens industry.

Soft disposable, spherical lenses were the first products of molding technology. They showcased the accuracy, capacity and speed of the new technology. Both eye health professionals and manufacturers recognized the opportunities for cost reduction, increased yield and improved consistency that molding offered.

The advantages of the disposable contact lens modality have positively influenced patient comfort and lens wearability in the spherical market for more than a decade. And beginning in the late 1990s, molding technology was applied in the area in which it was most needed -- for soft disposable toric lenses.

As mentioned earlier, rotational stability is perhaps the most important variable in fitting soft toric lenses successfully. This stability results from a good design and reproducibility in the manufacturing process. Molding creates consistency in lenses. Consistent quality soft toric lenses can now be produced in greater quantity and at higher quality levels than ever before, giving our toric soft contact lens patients the same advantages that our disposable spherical lens patients enjoy.

In addition, disposable soft toric contact lenses provide more consistent comfort and vision clarity, plus the opportunity to have a spare pair of lenses that, in the past, might have been cost-prohibitive.

THE FINAL INGREDIENT -- YOU

Today, we're no longer so limited by outside factors such as lens performance and lack of consistency. Instead, we limit ourselves. We don't recommend or prescribe soft toric lenses as much as we should.

Many of us don't fit soft toric lenses because we feel we don't have the time. Others have never become comfortable focusing on their expertise in fitting; they continue to be distracted by the sale of materials. But remember, our influence is paramount to a patient's willingness to try this modality, and paramount to their success or failure with it.

We must make the time to fit these contact lenses, focus on fitting them well and skillfully communicate with our patients about their benefits in correcting astigmatism. Doing so is in our patients' best interests, and our own, as well. 

Dr. West is in private practice in Brentwood, Tenn. He's the senior partner and chief operating officer of Primary Eyecare Group, a group practice providing optometric and ophthalmological services to middle Tennessee, southern Kentucky and northern Alabama.