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A Toric Lens that Offers Comfort and Consistency
BY JAMES W. KERSHAW, OD
Astigmatic patients have always been among our most challenging contact lens fits. In the old days we had to identify and compensate for lens rotation, then deal with patient complaints from inconsistencies in lens rotation. Even as toric contact lens designs have improved, we still face a higher risk of failure in this group.
The Acuvue Oasys for Astigmatism (Vistakon) lens has become my starting point for any patient who needs a toric lens because of its comfort and predictability. It orients on the eye more quickly and consistently than any other toric lens I've used. I find the lens straightforward to fit, approaching the ease of fitting we have with spherical lenses. By simply adjusting the prescription for the vertex I have a fit that is at least a good start and often is the endpoint.
Stability is Key
I believe Acuvue Oasys for Astigmatism has excellent optics. But we know that for astigmats, the best optics in the world can be useless if the contact lens rotates on the eye. Therefore, the quality of vision with a toric contact lens is more a question of the lens' stability on the eye than of the optics themselves.
Acuvue Oasys for Astigmatism has the same accelerated stabilization design (ASD) as Acuvue Advance for Astigmatism. The four-point stabilization system harnesses the natural pressures of a blinking eye to balance the lens in place.
When I tested Acuvue Oasys for Astigmatism before it was available commercially, we used a stopwatch to check alignment and found that when the lens is first placed on the eye it orients and stabilizes quickly in almost every case. Then, each time the patient blinks, the lens is pushed back into place for consistent vision throughout the day.
Unlike a prism-ballast or dual thin-zone lens, contact lenses with ASD don't interact with the lids when the eye is open; but with each blink or when the lens is misaligned, the lid forces come into play to "pinch" the lens back into place.
A recent study presented by Dr. Graeme Young at the 2008 American Academy of Optometry meeting in Anaheim, Calif., demonstrates how well this lens performs during unusual head positions and directions of gaze.
Fourteen subjects participated in the randomized, unmasked study in which four lens types were assessed. The lenses were Acuvue Oasys for Astigmatism, PureVision Toric (Bausch & Lomb), O2Optix Toric (CIBA Vision) and Proclear Toric (CooperVision).
In the first part of the study, subjects were positioned on their sides and the lenses were given time to settle. All of the lenses rotated in this recumbent position, but Acuvue Oasys for Astigmatism had significantly less rotation. The consequent mean reduction in visual acuity ranged from 0.05 logMAR for Acuvue Oasys for Astigmatism to 0.15 logMAR for PureVision Toric. It was significantly worse with PureVision Toric and Proclear Toric compared with Acuvue Oasys for Astigmatism (P<0.05).
In the second part, the subjects were positioned at a slit lamp and video recordings were taken as they changed their gaze from the primary position to each of the eight cardinal directions of gaze. Lenses tended to show nasal rotation on upgaze and temporal rotation on downgaze. The Acuvue Oasys for Astigmatism lenses showed significantly less rotation in a number of gaze directions than other lenses in the study, and particularly on inferio-nasal version where it rotated less than each of the other designs (P<0.005).
Adding in Comfort
Acuvue Oasys for Astigmatism is made from senofilcon A, and the Hydraclear Plus technology helps make this lens, like its spherical counterpart, comfortable. In my practice patients immediately recognize how good it feels from the first time they put on the lens.
"I think comfort is a huge advantage of this lens," says Teri Geist, OD, who is in private practice in Omaha, Neb. She is finding success prescribing Acuvue Oasys for Astigmatism for patients who have given up lens wear or for wearers struggling due to dryness and discomfort.
"We think of ocular dryness as primarily affecting older, postmenopausal women, but there is an epidemic of dry eye in younger women, too," Dr. Geist says. "In my practice, I see a lot of young women who are having trouble tolerating contact lenses, whether it's because of long hours at a computer, lack of sleep, or medications like birth control pills and antihistamines. Acne medications can also destabilize the tear film, even years after the patient stops using them."
She cites one particularly challenging patient, a 35-year-old female who has low astigmatism (0.75D), spends a lot of time using a computer, and has a history of Accutane use. Recently, she complained of end-of-day headaches at work.
"Although we have tried a number of toric lenses over the years, I have never found one that she can wear comfortably until Acuvue Oasys for Astigmatism," says Dr. Geist. "With the comfort of Hydraclear Plus technology, I've finally been able to fit her with an astigmatic lens that satisfies both her comfort and visual demands. The headaches also seem to have disappeared now that she has crisper vision for work."
In addition to the comfort, Dr. Geist says the lenses are also easy to handle. The lenses aren't curled up in the pack so they are easy for patients to remove, clean, and put in the eye.
For me, UV protection is an important consideration in a lens. In June 2008, Acuvue Oasys for Astigmatism received a Seal of Acceptance for Ultraviolet Absorbing Contact Lenses from the American Optometric Association's Commission on Ophthalmic Standards. It offers the highest level of UV-blocking available, blocking more than 90 percent of UV-A rays and 99 percent of UV-B rays that reach the lens. On average, contact lenses without UV blocking block approximately 10 percent of UV-A radiation and 30 percent of UV-B radiation.
Talk about the harmful effects of UV radiation is pervasive in the media and in advertising for everything from skin creams to window treatments. Patients readily understand that UV light is bad, so it is nice to be able to offer them a contact lens that, along with sunglasses and hats, can help protect their eyes from UV light.
A Nice Niche
Of course, no lens — much less a toric — is going to work for every patient. There will be some for whom the base curve, diameter or power range isn't quite right.
But what I'm looking for most of all in a toric lens is a predictable fit. With Acuvue Oasys for Astigmatism, I find that if the patient has comfort and vision in the office, and if the lens seems to have appropriate movement and orientation when I examine it on the eye, the chance of success is high. In fact, I don't recall a case where I sent the patient home in this lens and it hasn't worked out.
That predictability cuts down on chair time, which is important to the bottom line. Equally important for anyone in private practice is that providing efficient care that makes patients happy can create a sense of prestige and confidence.
Acuvue Oasys for Astigmatism is a great contact lens for those patients who might have been getting by with a spherical correction, especially if the astigmatism is a large portion of the total correction. A low myope or hyperope may benefit greatly from a toric correction, and with this lens they won't have to give up the comfort they had with a spherical lens.
I believe we have to give patients a reason for coming in to the office by exposing them to new products that may offer benefits over their current contact lenses. Although I'm not necessarily changing every astigmatic patient over to this lens, I'm not shy about offering a trial. If I can give them crisper or more comfortable vision it will only improve their experience with contact lens wear and with our practice. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #161.
Dr. Kershaw is in private group practice in North Olmsted, Ohio. He is also serves on advisory boards for Hoya North America and Vistakon. Contact him at (440) 734-4777 or email@example.com.