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Contact lenses can reduce aberrations
Contact Lenses and Eyewear
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When it comes to helping patients reduce optical aberrations, practitioners can choose from a variety of contact lenses. Wavefront diagnostic technology is often the catalyst for these vision improvements.
PureVision lenses
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The PureVision silicone hydrogel from Bausch & Lomb (Rochester, N.Y.) is an aspheric contact lens that corrects for spherical aberration. “This lens offers some of the best acuity, especially in regard to quality of vision and nighttime vision,” Paul M. Karpecki, OD, director of research in Cornea and External Disease Service at Cincinnati Eye Institute, said in an interview with Primary Care Optometry News.
“A patient who drives a truck at night or is an avid golfer is provided with the highest acuity possible,” he continued. “This would be my lens of choice. Even though 20/20 is the ability to discern letters, equally important are contrast sensitivity levels and the ability to correct aberrations that affect vision with nighttime or distance.”
The PureVision lens has a correction factor for degree of power desired. “However, this lens is not wavefront guided; it is wavefront enhanced,” Dr. Karpecki, also a PCON Editorial Board member, said. “Spherical aberration is the same in any axis, so you can correct for it in a contact lens. But you could not necessarily correct for all the aberrations.”
In his own research measuring eyes with various aberrometers before and after correction, Dr. Karpecki found a significant decrease in spherical aberrations.
Another application of wavefront enhancement is the PureVision Multifocal Contact Lens. “Although this lens uses aberration-like aspherics, it is a slightly different mechanism,” Dr. Karpecki said. “A little bit of negative asphericity is created within the lens to help with accommodation.”
Candidates for the PureVision Multifocal are patients older than 43 and those who are presbyopic. “Adding that negative sphericity change will enhance overall vision slightly more than by just adding power,” Dr. Karpecki said. “Negative or neutral sphericity as opposed to positive asphericity also helps increase depth of focus.”
In the future, Dr. Karpecki predicts more customization like these two Bausch & Lomb lenses. “I envision the ability, in quick time, to measure a patient’s cornea for aberrations then create a lens based on those measurements,” he said. A computer would forward the measurements to a laboratory, and the lenses would be returned immediately.
The challenges with using the patient’s unique wavefront profile to create custom contact lenses are “movement and the ability to then stabilize that lens, so you are correcting only in that one place,” Dr. Karpecki said. “Given our current situation, I think wavefront-optimized — such as correcting aspheric optics — makes a lot of sense. But longer term, we will continue to find ways to enhance quality of vision in customizing the lenses. There is probably a solution in the middle, where you maximize both the aspheric surface and the patient’s own wavefront profile in a system that has minimal movement.”
CooperVision daily disposable
CooperVision (Rochester, N.Y.) uses front-surface aspheric designs to control spherical aberration. For instance, the Proclear daily disposable is a hydrogel aspheric lens introduced earlier this year in the United States that “corrects the spherical aberration of the lens and the eye,” Arthur Back, BOptom, PhD, vice president of product development at CooperVision, said in an interview.
On the other hand, the Biofinity lens is made of a silicone hydrogel material that also corrects the spherical aberration of the contact lens and the eye. The Biofinity lens will be launched in the United States mid-2007.
“We feel that by correcting both elements of those higher-order aberrations – the lens and the eye – we achieve superior vision performance, particularly in low-light conditions,” Dr. Back said.
The basic optical design of the Proclear daily disposable is the same as the Biofinity lens. “The Proclear allows us to correct the spherical aberration of the contact lens, while at the same time correcting the spherical aberration that is inherent in the eye,” Dr. Back said. The Proclear is especially beneficial in lower-lighting conditions with larger pupil sizes and with higher prescriptions.
“The daily disposable is more convenient for patients because they don’t need a lens care system,” Dr. Back said. “In addition, the Proclear is the only hydrogel lens on the market approved by the Food and Drug Administration to alleviate dryness.”
A third lens from CooperVision, the Biomedics XC, has an aspheric design that corrects the aberration of the lens only.
The company is researching aspheric design technology to help patients with astigmatism and presbyopia. “The goal is to reduce aberrations in these two types of contact lens wearers,” Dr. Back said.
SynergEyes lenses
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The SynergEyes A (ametropia) from SynergEyes Inc. (Carlsbad, Calif.) is a hybrid lens with a spherical gas-permeable (GP) center and 27% water soft skirt. “Basically, the A lens will correct refractive astigmatism that is equal to corneal astigmatism,” Dianne M. Anderson, OD, an optometrist at LensCrafters in Aurora, Ill., told PCON. “Compared to a soft toric lens, which might rotate on the eye, there is less aberration with the GP center of the SynergEyes lens. This hybrid lens is fit 1 D to 2 D steeper than the flat K reading and allows less aberration by masking up to approximately 1.75 D of corneal and refractive cylinder.”
For additional astigmatic correction, the SynergEyes EP (enhanced profile) lens has an increased GP center thickness, which allows for “nearly a doubling of the amount of correctable astigmatism, up to about 3.50 D of corneal cylinder,” Dr. Anderson said.
The SynergEyes KC (keratoconus) is a back-surface aspheric GP lens with a 27% water soft skirt. “This hybrid lens centers better over the pupil, as compared to most standard GP lenses,” Dr. Anderson said. “This reduces aberration that is caused by decentered lenses in many cases of keratoconus.”
The SynergEyes PS (postsurgical) is a reverse geometry GP lens for oblate corneas, such as post-LASIK or post-radial keratotomy (RK). “This lens generally targets post-refractive surgical patients and some cases of post-penetrating keratoplasty,” Dr. Anderson said. “In many of these situations, most of the problem is caused by postsurgical aberration on the corneal surface. The PS lens will match that surface because it is flatter in the center. The steeper skirt will also match their peripheral cornea.”
Overall, each of these SynergEyes lenses “greatly improves quality of vision and patient comfort because they do not feel like a GP lens on the eye,” Dr. Anderson said. “Most patients with aberrations induced by soft toric lens rotation or poorly fit GP lenses are much happier in SynergEyes.”
C-Vue Aspheric Single
Vision lens
Since its debut in February 2006, the C-Vue Aspheric Single Vision lens from Unilens (Largo, Fla.) has been frequently dispensed by James A. Muse, OD, who practices in Ocala, Fla. “To date, I’ve fit close to 50 patients with this lens,” he said.
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The C-Vue features a wavefront-assisted aspheric design that is not individually customized.
“This lens helps monovision patients with their night driving,” Dr. Muse told PCON in an interview. “Higher-order aberrations often come into play with changes in pupil size. People who wear monovision contact lenses tend to complain about their vision at night because their pupil dilates.”
In addition, patients with a minimal amount of astigmatism or who are not presbyopic (e.g., myopes or hyperopes with low astigmatism) “tend to do a little better with the C-Vue, without having to correct for the astigmatism,” Dr. Muse said.
The C-Vue, a hydrogel lens, should be an adjunct to other lenses in one’s arsenal. “You should consider all types of wavefront technology contact lenses because of other issues patients may have, such as dryness or comfort or breathability,” he said.
Dr. Muse encourages his colleagues to consider fitting aberration-reducing lenses more often. “Just because a patient sees well on a white chart with black letters does not necessarily carry over to excellent vision for driving at night or in the rain, or other circumstances where the environment tends to influence vision,” he said. “The goal is to eliminate all visual distortions that can affect overall vision.”
WaveTouch lenses
WaveTouch is a new wavefront-guided soft contact lens from WaveTouch Technologies (San Jose, Calif.). “The basic premise behind the lens is that an optometrist or an ophthalmologist can take wavefront aberrometry readings of the patient in his or her office with one of several aberrometers,” Sandra M. Zuccaro-Keyes, FNAO, NCLC-AC, an advanced certified contact lens fitter for WaveTouch Technologies, told PCON. The fitter then forwards the individualized wavefront aberrometry reading by fax or electronically to the company’s lens manufacturing facility in San Diego.
The soft lens that is produced “will help correct lower-order and higher-order aberrations,” Ms. Zuccaro-Keyes said. “In the lower order, it would correct sphere and cylinder, while in the higher order it would aid in the correction of aberrations such as coma and spherical aberration. The WaveTouch lens is revolutionary for the doctor because while the fitting will be simple; the correction for the patient will be remarkably advanced compared to what the doctor can do today. In addition, the patient is tied to the practice because of the individualized custom nature of the patient’s treatment. The feedback from patients has been exceptional.”
Ms. Zuccaro-Keyes’ father is Vincent Z. Zuccaro, OD, FAAO, chairman of WaveTouch Technologies. Both father and daughter helped form the company. The patented WaveTouch Process manufacturing process and the intellectual property licenses surrounding wavefront-guided contact lenses were recently purchased from Optical Connection, along with the custom soft and GP business. Optical Connection continues to market its line of soft disposable contact lenses under the Definition name.
Currently, the WaveTouch soft lens, designed from in-office aberrometry readings, is made from methafilcon A, with a 55% water content. “This is a tried-and-true material that is extremely stable in its fitting characteristics,” Ms. Zuccaro-Keyes said. Studies utilizing various aberrometers to provide the necessary information for the WaveTouch Process are ongoing, and a number of commercially available aberrometers have been certified to date. WaveTouch Technologies is continuing this portion of the clinical process and expects to roll out WaveTouch contact lenses into the market later this year.
For more information:
- Paul M. Karpecki, OD, FAAO, is director of research in Cornea and External Disease Service for Cincinnati Eye Institute and a member of the Editorial Board of Primary Care Optometry News. He can be reached at 580 S. Loop Rd., Ste. 200, Edgewood, KY 41017; (859) 402-2814; fax: (859) 331-9040; e-mail: paulk-vc@kc.rr.com. Dr. Karpecki is a paid consultant for Bausch & Lomb.
- Arthur Back, OD, PhD, is vice president of product development at CooperVision. He can be reached at 5870 Stone Ridge Dr., Pleasanton, CA 94588; (925) 251-6644; e-mail: aback@coopervision.com.
- Dianne M. Anderson, OD, can be reached at LensCrafters, 1298 Fox Valley Center, Aurora, IL 60510; (630) 851-8302; fax: (630) 851-8329; e-mail: dianne.anderson@comcast.net.
- James A. Muse, OD, can be reached at 5400 Southwest College Rd., Ste. 106, Ocala, FL 34474; (352) 622-3937; fax: (352) 861-1177; e-mail: museumeyecare@earthlink.net. Neither Dr. Anderson nor Dr. Muse has a direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.
- Sandra M. Zuccaro-Keyes, FNAO, NCLC-AC, an advanced certified contact lens fitter at WaveTouch Technologies can be reached at 1975 Hamilton Ave., Ste. 1, San Jose, CA 95125; (408) 694-3958; fax: (408) 694-3976; e-mail: szkeyes@wt-lens.com.
- Bausch & Lomb can be reached at 1400 Goodman St., Rochester, NY 14609; (585) 338-5212; fax: (585) 338-0898; Web site: www.bausch.com.
- CooperVision can be reached at 370 Woodcliff Dr., Ste. 200 Fairport, NY 14450; (800) 341-2020; fax: (800) 209-0154; info@coopervision.com; Web site: www.coopervision.com.
- SynergEyes can be reached at 2232 Rutherford Rd., Carlsbad, CA 92008; (760) 476-9410; Web site: www.synergeyes.com.
- Unilens can be reached at 10431 72nd St. North, Largo, FL 33777; (727) 544-2531; fax: (727) 545-1883; Web site: www.unilens.com.
- WaveTouch Technologies can be reached at 1975 Hamilton Ave., Ste. 1, San Jose, CA 95125; (408) 694-3958; fax: (408) 694-3976. A Web site is under construction.