Torics for Astigmatism: Soft Lenses, Hard Choices
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Today’s soft toric designs and materials offer better optics, improved stability, a wider range of stock parameters and the option of daily disposability. “Additionally, there are a number of smaller niche laboratories making more custom-parameter lenses now than in the past, so we have a lot of choices for people who might not fit into one of the disposable types of lenses,” says Douglas Benoit, OD, of Concord, NH. Thus, the challenge in fitting astigmatic patients is no longer a dearth of options, but ratherwhichoption to choose from the wide variety now available.
Increased chair time and patients’ financial reservations are noteworthy obstacles as well—but the one justifies the other, successful practitioners say. If you’re adept at giving astigmatic patients crisp vision, they’ll be more willing to pay for the additional cost of toric lenses and your professional expertise in fitting them.
Let’s take a look at some of the new advances and how they can improve care for your astigmatic patients.
Changes in Soft Torics Silicone hydrogels and daily disposables—the newest players in the soft toric lens market—now provide a fairly substantial parameter range, offer greater ease in fitting and have better predictability, stability and reproducibility than previously, says Glenda Secor, OD, a private practictioner in Huntington Beach, Calif.
•Silicone hydrogels.These lenses now account for more than 80% of new toric soft lens fits in the United States.2 They are a popular option because silicone materials have been shown to decrease the likelihood of complications, such as hyperemia, dryness and discomfort.3 Silicone hydrogels also enhance oxygen transmissibility, which can prevent corneal neovascularization due to low oxygen tension beneath the thick prism ballast of a toric hydrogel lens design, says Steven Grant, OD, of Costa Mesa, Calif. In the past few years, manufacturers have ushered in a number of new silicone hydrogel lenses for astigmatic patients with improved stabilization designs.
•Daily disposables.“The advent of daily soft torics has dramatically improved convenience for patients who want a more frequent replacement option, especially when they go swimming or play sports,” says optometrist Robert Grohe of Chicago. Daily disposable toric lenses first arrived on the market more than a decade ago and the options have continued to increase since, providing astigmats more convenience without sacrificing efficacy. Studies have shown that disposable toric lenses provide the same visual acuity, centered fit and comfort as daily-wear lenses, but with fewer deposits and less ocular reactions.4
•Expanded parameters.Despite the proven clinical efficacy of soft torics in astigmats, optometrists often had a difficult time finding the right fit in the past due to limited parameters. However, recent advances in soft torics have added more cylinder power and axis options, enabling ODs to help a wider range of astigmatic patients.
“Cylinder power in the past used to go up to about -1.75 to -2.25, but lately, the cylinder powers have been expanding up to the four- to five-diopter range,” Dr. Grohe says. “While high cylinder prescriptions are more complicated, these are very motivated patients who benefit from the expanded parameter options and more precise vision.”
• Multifocal soft torics.In the past, astigmatic patients with presbyopia had little option but to wear reading glasses over their contact lenses. But today, patients now have more freedom with lenses that combine correction for both astigmatism and presbyopia. Researchers have found that multifocal soft torics provide optimal distance and near vision quality without compromising stereopsis.5
In addition to a few options from large manufacturers, several custom laboratories also manufacture conventional soft toric multifocal contact lenses. “As optics continue to improve, I think multifocal soft torics are going to be a growth opportunity for the future,” Dr. Grohe says.
•Niche labs. For difficult-to-fit patients, a number of laboratories can produce custom-lathed soft toric contact lens options with hydrogel materials. Dr. Benoit says his go-to specialty labs produce custom toric soft lenses with expanded parameters that the larger manufacturers are not currently offering. “These smaller labs have increased what we can do, so more patients are able to wear toric soft contact lenses than in the past,” he says.
A more recent addition to the market, Definitive (efrofilcon A, Contamac) is a latheable made-to-order, daily-wear silicone hydrogel material, which works well for high astigmatic patients wishing to wear soft lenses. It is now available through a number of specially authorized labs.
•More stable lens designs.“In the past five or six years, we have seen much more stability and predictability with soft toric lenses,” says optometrist Jeffrey Krohn of Fresno, Calif. In fact, research has confirmed it. Clinicians at Indiana University studied the rotational fitting characteristics of five toric lenses and found 10° or less rotation with 95% of the lenses and less than 5° of rotation with 80% of the lenses.6
“Before, we were making a lot of calculations because we were observing 15°, 20° or even 30° of rotation on a fairly routine basis,” Dr. Krohn says. Newer advances in design, he says, give doctors more confidence in ordering diagnostic lenses. “We put the lenses on and know we are going to be pretty close.”
Spherical or Soft Toric?
ODs have often turned to spherical lenses in the past because they have few, if any, rotational issues; however, they are not designed to provide astigmatism correction and toric lenses have since improved considerably. Some patients with low levels of astigmatism can tolerate spherical lenses, but at which point is it best to fit a soft toric instead of a spherical lens? “I think once you get above 0.75D of astigmatism, if the patient’s spherical component is below plus or minus four, you should really be thinking about a soft toric as opposed to a sphere,” Dr. Benoit says. “And if a patient’s distance component is greater than a plus or minus four, when they get to about 1.25 cylinder, you really need to consider (a
Dr. Secor agrees about the -0.75 cylinder threshold as a general principle, but says it should be even less in patients with vertical or oblique astigmatism. Because with-the-rule astigmatism is more forgiving with uncorrected cylinder, 0.70D of cylindrical correction must be present before she will fit a toric lens. Dr. Grohe agrees that more patients will probably find a greater tolerance in a soft toric if they have with-the-rule astigmatism, while those with against-the-rule and oblique astigmatism may have narrower success.
Another question that often arises with soft torics vs. spherical designs: Can an OD use the spherical equivalent as opposed to using the actual prescription? In the past, when cylinder powers were limited, this was a necessary evil. “Today we can give the patient a more precise trial soft toric lens and see how he or she does,” Dr. Grohe says. Usually, the outcomes are quite positive. Recent research has shown that astigmats achieve better visual acuity when refitted with toric soft lenses compared to spherical contact lenses.1
|Wish List for the Future|
While the toric soft lens market has greatly expanded, doctors still have a few wish-list items for the future. Dr. Grohe would like to see more companies use lens polymers that contain UV absorbent technology, while Dr. Benoit hopes to see the use of silicone hydrogel materials increase.
“With silicone products, you don’t have to worry about oxygen flow to the cornea. The big concern 30 years down the road—after a person has worn lenses all that time—is whether or not there will there be problems because they aren’t getting enough oxygen,” Dr. Benoit says. “Having a lens that is able to deliver more oxygen is really beneficial.”Other items include expanded options in high cylinders, oblique axis and multifocal torics. And high on many doctors’ lists is the development of a silicone hydrogel daily disposable toric. If the rapid advances in toric material and design over the past few years are any indication, these dreams could very well become reality in the near future.
When GP is the Way to Go
If a patient has astigmatism and needs a bifocal or multifocal contact lens, Dr. Benoit finds gas permeable designs are generally superior. “With that said, there are a number of laboratories making soft lenses that correct astigmatism and include a bifocal as well,” he says.
Dr. Secor typically prescribes a GP design if the corneal cylinder is equal to the refractive cylinder, especially on with-the-rule corneas. She also finds gas permeable lenses to be a good option for highly allergic patients because they tend to stay cleaner and proteins don’t adhere to them as easily as they do to soft lenses.
If a patient has irregular astigmatism or is currently happy in their gas permeable lens, Dr. Grohe will go with the GP instead. He also recommends GPs for patients with corneal disease or keratoconus, as well as those who have undergone penetrating keratoplasty. “In the face of new soft toric products, the GP industry will need to counter with a continued commitment to developing new materials and solutions,” he says.
Improved Patient Care
Of course, one of the biggest improvements in the newer soft toric designs is better vision. “We have the term ‘masking astigmatism,’ which I’m not a fan of,” Dr. Grant says. “If I have a patient with 20/25 vision or 20/30 vision and I can now give them 20/20 vision, I think it’s incumbent on me to provide the best vision possible, and it reduces the dropouts.” He’s also found that the expanded parameters and low cylinders of the new soft torics have satisfied the previously unmet needs of certain patients and, in turn, allowed for much better visual comfort.
Some doctors have found that the increased options in daily soft torics have helped eliminate problems such as solution sensitivity and irritation to the cornea or lids. “Daily disposables fortunately increase compliance quite a bit because there is nothing simpler than just throwing the lens away after one use,” Dr. Benoit says.
All of these new developments in toric soft lenses have helped streamline the fitting process. “Patients these days are interested in getting the best care, but they are not interested in spending hours in the office,” Dr. Grohe says. “New improvements in lenses minimize the amount of chair time that was once traditionally needed.”
In the past, Dr. Grohe often found soft toric fitting laborious—insert lens, wait 30 minutes for it to settle, take measurements, then make adjustments based on rotation or mislocation. “With the new lens designs and improved manufacturing, lens performance has become more dependable,” he says. “You can put a lens on a patient, know it is more predictable and get more stable visual acuity in a shorter period of time.”
1. Sulley A, Young G, Lorenz KO, Hunt C. Clinical evaluation of fitting toric soft contact lenses to current non-users. Ophthalmic Physiol Opt. 2013 Mar;33(2):94-103. 2. Nichols JJ. Annual report: contact lenses 2011. Cont Lens Spect. 2012 Jan;27(1):20-5. 3. Dumbleton K, Keir N, Moezzi A, et al. Objective and subjective responses in patients refitted to daily-wear silicone hydrogel contact lenses. Optom Vis Sci. 2006 Oct;83(10):758-68. 4. Cabrera JV, Rodriguez JB. Vision with disposable toric contact lenses and daily-wear toric contact lenses. Ophthalmic Physiol Opt. 1998 Jan;18(1):66-74. 5. Madrid-Costa D, Tomas E, Ferrer-Blasco T, et al. Visual performance of a multifocal toric soft contact lens. Optom Vis Sci. 2012 Nov;89(11):1627-35.
6. Andrzejewski TM, Pence N. Design, materials and fitting of toric silicone hydrogel lenses. Cont Lens Spect. 2011 Sep;26(9):32-7.