IS THIS THE NEW NORM?
ARE FITTING SOFT LENSES THE NEW NORM FOR HIGH ASTIGMATISM?
MILE BRUJIC, OD, FAAO, & DAVID L. KADING, OD, FAAO
We’ve all seen the high astigmatic patient who is a first-time contact lens wearer who has worn contact lenses in the past and then dropped out, or who is currently wearing contact lenses but is unhappy because of fluctuating vision.
Although the designs to which we currently have access for our patients have a high level of predictability, high-cylinder patients are much more attuned to small rotations in the lens. In particular, individuals who have greater than 3.00D of astigmatism are often the patients who present a unique challenge.
So, what options do we have to better correct the vision of these individuals? Luckily, we have several options available.
1) GP Lenses These have always been the standard against which vision is compared. One of the concerns that many have is the initial lens awareness that our patients may experience when being fit with GPs. Some of this awareness may be mitigated by using a lens that is slightly larger than what we would typically select. Oftentimes, the initial diameter that a practitioner may select for a patient is between 9.0mm and 9.6mm. By considering slightly larger diameters, such as those >9.6mm, there will be less lens movement and often less initial lens awareness (Figure 1).
Figure 1. A 10.3mm GP lens fit on a patient who has 2.00D of with-the-rule astigmatism.
Additionally, it is important to be comfortable with back-surface toric and bitoric lens calculations. An extremely valuable, user friendly online resource for this can be found on the GP Lens Institute website (www.gpli.info/lens-calculator).
2) Hybrid Lenses Although these lenses have been available for some time, the fitting process has become much more streamlined in recent years. Newer hybrid lenses have a high-Dk GP center and a silicone hydrogel skirt, which delivers the optics of a GP while providing the fit characteristics and reduced lens awareness similar to a soft lens.
The empirical fitting process makes it a streamlined approach. A patient’s spectacle prescription along with keratometry readings are used to order lenses for patients. This streamlined approach provides a simplified way for practitioners to provide hybrids to their patients.
3) Scleral Lenses Although often considered a GP lens because of the material in which they are made, these lenses are fit completely differently because they clear the cornea. The optical correction is created through the optics in the lens as well as through the preservative-free solution that is between the posterior surface of the lens and the anterior cornea. Although we typically think of scleral lenses for those who have irregular corneas, keep them in mind for individuals who have high levels of astigmatism.
We are fortunate to have a number of soft toric options readily available in daily disposable, two-week, and monthly replacement modalities. And for those who have astigmatism at higher levels, we also have custom soft toric lens options available in both hydrogel and silicone hydrogel materials. But, when visual stability isn’t being met by soft toric lens options, remember the available GP options. If fitting soft toric contact lenses for all patients who have astigmatism is the new normal, we don’t want to be normal. CLS
Dr. Brujic is a partner of Premier Vision Group, a three-location optometric practice in northwest Ohio. He has received honoraria in the past two years for speaking, writing, participating in an advisory capacity, or research from Alcon Laboratories, B+L, Bruder, Optovue, RPS, SpecialEyes, and VMax Vision and has received research funding from Optovue and SpecialEyes.
Dr. Kading owns the Specialty Dry Eye and Contact Lens Center in Seattle. He is the co-owner of Optometric Insights with Dr. Mile Brujic. He has received honoraria for consulting, performing research, speaking, and/or writing from Alcon Laboratories, Allergan, Bausch + Lomb, CooperVision, Johnson & Johnson Vision Care, Oculus, OptoVue, RPS Detectors, Paragon Vision Sciences, TearScience, Valeant Pharmaceuticals, Valley Contax, VSP, ZeaVision, and Zeiss. Follow him on Twitter @davekading.