In this installment of Interventional Mindset, Gary Wörtz, MD, speaks with Preeya K. Gupta, MD, about methods for managing astigmatism, including using a femtosecond laser.
Astigmatism has always been a bit of a mysterious condition to treat, Dr. Wörtz begins: when he first started as an ophthalmology resident, he didn’t think about correcting astigmatism until a patient had about a diopter or more.
However, with time and the more widespread implementation of the femtosecond laser, he realized that there was now a new tool and opportunity to treat patients with lower-level astigmatism who wouldn’t necessarily benefit from a toric lens.
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Using the femtosecond laser to treat lower-level astigmatism
Astigmatism management is rarely straightforward, notes Dr. Gupta. Higher levels of astigmatism will clearly benefit from toric IOLs, but lower levels of astigmatism are still a valuable area of focus for practitioners.
In a paper co-authored by Dr. Gupta and Wörtz, they showed that managing low levels of astigmatism (less than a diopter) leads to more patients achieving 20/20 uncorrected visual acuity. Intervening earlier in astigmatic patients and using a femtosecond laser caused almost a 200% increase in 20/20 uncorrected patients and over a 350% increase in uncorrected 20/25 visual acuity at the end of treatment.
Dr. Wörtz mentioned that prior to the study, he observed that patients undergoing cataract surgery with a monofocal lens and femto arcuate incisions were getting very close to plano sphere after undergoing the femtosecond laser procedure. But it wasn’t until he looked at the data from the study that this hunch was confirmed; treating lower levels of astigmatism, and having a plan for those patients, gives them the refractive outcome they are looking for.
Identifying tools for treating lower-level astigmatism
One of the key issues clinicians encounter when treating astigmatism is deciding which treatment modality to choose. There are so many potential approaches for treating astigmatism that it’s almost a paradox of choice.
Dr. Gupta broke down her process for treating an astigmatic patient that helps combat this problem. Before even walking into a patient’s room, she looks at their topography and biometry using the Zeiss IOL Master 700. Then she looks at the patient’s magnitude and axis of astigmatism to gauge what tools may be needed to full address the astigmatism at the time of cataract surgery.
For patients with higher levels of astigmatism, she leans towards using a toric lens, but for lower levels, she often uses the femtosecond laser to create arcuate incisions. During the procedure, optical coherence tomography (OCT) is used to place the incisions, allowing for, in Dr. Gupta’s opinion and experience, a more precise shape and depth compared to manual limbal relaxing incisions.
From a corneal perspective, a key thing to look for is if the patient has any corneal irregularities, such as Fuchs dystrophy, pterygium, anterior basement membrane dystrophy (ABMD), or anything that could contribute to irregular astigmatism. For any patient with a normal cornea and low levels of astigmatism, Dr. Gupta’s process from there is to use a femtosecond laser.
Using the Wörtz-Gupta Formula for femtosecond laser procedures
Dr. Gupta and Dr. Wörtz put together the Wörtz-Gupta Formula, which is a femtosecond laser arcuate incision formula. It is freely available at www.LRIcalc.com and requires only three input variables—patient age, location of steep axis, and magnitude of astigmatism. This formula is the first to be specifically designed for femtosecond laser-assisted arcuate incisions.
Prior manual limbal relaxing incision formulas have been attempted to be adjusted but not validated with femtosecond laser usage. The formula has only been studied for correction of corneal astigmatism <1.25D using a femtosecond laser at a 9.0mm optical zone and 80% depth, opened manually at the time of cataract surgery.
A unique feature of this calculator is that the incision is held constant (always at 0 or 180), so it was designed to show the procedure from a temporal approach. This calculator helps to simplify the complexities of determining the most effective arc length and also validates the importance of treating lower levels of astigmatism. Astigmatism management, Dr. Gupta argues, is something that should be considered with every patient. The capabilities of the femtosecond laser support this attention.
Conclusion
Using the femtosecond laser to treat patients with lower-level astigmatism shows the value of having an interventional mindset as a surgeon. By proactively identifying astigmatism and treating it at the time of cataract surgery, patients will have improved uncorrected acuity.
Adopting the femtosecond laser for arcuates and implementing the Wortz-Gupta formula has simplified our abilities to provide that excellent uncorrected vision that patients desire. So if you haven’t checked out www.LRIcalc.com, try it on your next few cases.
Ultimately, this is the focus and goal of the Interventional Mindset series: to disseminate knowledge, experience, and resources to fellow surgeons to get the best possible patient outcomes.
