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Toric options benefit patients, surgeons
Expanding toric IOL options for patients with astigmatism should be a top priority.
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The majority of patients presenting for cataract surgery have at least 0.5 D of astigmatism. Although it is true that we can get many of these eyes to emmetropia simply by making the entry wound on the steepest axis, there is still a large segment of the population with more significant astigmatism. According to an analysis of more than 23,000 eyes, 36% of the cataract population has 1 D or more and 17% has 1.5 D or more of corneal astigmatism.
For these patients, a spherical lens without limbal relaxing incisions (LRIs) or astigmatic keratotomy is unlikely to offer good uncorrected distance vision, and the precision of the refractive result leaves something to be desired.
Toric IOLs, therefore, have been a wonderful addition to our armamentarium of IOLs. Since they were first introduced more than a decade ago, toric lenses have allowed us to reliably offer astigmatic patients the same high-quality, predictable distance vision without spectacles that we can provide for our spherical patients.
The toric options that we currently use include the AcrySof IQ toric (Alcon), a one-piece hydrophobic acrylic IOL, and several models of the STAAR toric plate lens. Recently, another one-piece lens for astigmatism, the Tecnis toric (Abbott Medical Optics), was added to the list.
Marjan Farid
Sumit “Sam” Garg
We do not yet have personal experience with the Tecnis toric IOL, but because we often implant toric IOLs — about 150 annually — it is exciting to see new options.
One-piece clear optic
A one-piece lens with a clear optic has long topped our wish list for toric lenses. Currently, surgeons have to choose between a plate toric with a clear optic and a one-piece toric lens with a yellow chromophore. The initial rationale for the yellow lens was that it would protect the aging eye by blocking blue light. However, there is no clear-cut evidence of a protective effect against macular degeneration.
It is not unusual for a patient to need a toric IOL in one eye only. In such cases, we are reluctant to implant a yellow toric lens in the second eye of a patient who has already had an IOL with a clear optic implanted in the first eye, simply to avoid any noticeable difference in color vision or contrast between the two eyes.
Other features of the Tecnis one-piece platform that we look forward to include the aspheric design of the lens, and the ease of implantation and centration.
Expanding range
With the current lenses on the market, we have seen some extension of the dioptric range. An extended dioptric range up to 6 D or 8 D could be useful for that small percentage of eyes with high natural or post-PK regular astigmatism. We already implant toric lenses in such eyes and find that even reducing the astigmatism by half sometimes makes it possible for patients to achieve spectacle freedom. If not, it can open the way for other surgical options, such as PRK or astigmatic keratotomy.
At the other end of the range, it is likely we will see some lower power toric lenses in the U.S. It is not clear, however, whether the refractive effect of lower power lenses will be as predictable.
Ultimately, both surgeons and patients will benefit from having more toric IOL options. Just as we do not rely on a single standard monofocal or presbyopia-correcting IOL to suit all patients, we cannot expect a single toric lens to meet the needs of all patients either.
Astigmatic patients will continue to be a large and important segment of the cataract patient population, and we should push ourselves as surgeons to achieve the same emmetropic results in these patients that we strive for in other patients. As new technologies such as femtosecond laser-assisted cataract surgery and intraoperative wavefront aberrometry continue to advance our capabilities to treat astigmatism, it is important to keep pushing the boundaries of toric IOL technology as well.