As more and more patients expect refractive outcomes after cataract surgery, surgeons are having to pay closer attention to the state of the cornea. Dr. Singh sat down with Gary Wörtz, MD, to talk about astigmatism—how much correction makes a difference in vision; the best treatments for various amounts; and how to talk with patients about their visual goals so they can deliver the results they want.
To kick off their discussion, Dr. Singh asked Dr. Wörtz why it’s important to not ignore astigmatism, and why (and how) he treats low astigmatism.
It is generally estimated, Dr. Wörtz said, that half of those with visually significant astigmatism (1.00 D or more) are going untreated. “That causes blurry vision, reliance on spectacles, and a suboptimal outcome, if we’re talking about cataract surgery as a refractive procedure,” he added. He estimated that 75% of patients seeking cataract surgery have between 0.25 D and 0.75 D of astigmatism, and it is unknown how many of these individuals are untreated.
When it comes to IOL implantation, astigmatism can impact the outcome. “There have been studies that show that, especially in a multifocal lens, residual astigmatism is exponentially more important than even in a spherical lens,” Dr. Wörtz told Dr. Singh. It’s well known, Dr. Wörtz said, that patients with multifocal implantations and 0.75 D of astigmatism usually need a LASIK touch-up or some other refractive correction. “We know the visual detriment of astigmatism, and if we can treat it, we should figure out a way to do so,” he commented.
In his own practice, Dr. Wörtz said he tries to eliminate astigmatism as much as possible to give patients their best vision—from 0.25 D upward. “Just like with glasses, we wouldn’t leave astigmatism uncorrected,” he reasoned.
Low Astigmatism Retrospective Study
One potential challenge in correcting low astigmatism (<1.00 D) is that the various nomograms available for surgical use are based on eyes with greater than 1.00 D of astigmatism. To answer this unmet need, Dr. Wörtz worked with Preeya Gupta, MD, to develop the Wörtz-Gupta formula, an arcuate incision nomogram specifically designed to treat astigmatism of <1.00 D in eyes that aren’t candidates for a toric IOL. In addition to being freely available at www.lricalc.com, the nomogram is built into the VERACITY surgery planner by ZEISS.
Drs. Wörtz and Gupta recently published a retrospective review of 224 patients who had <1.00 D of preoperative corneal astigmatism before undergoing cataract surgery.1 Patients were divided into two groups: (1) those who had elected femtosecond laser-assisted cataract surgery (FLACS), which included the surgical correction of their astigmatism using the Wörtz-Gupta formula (n = 124); and (2) those who had chosen standard cataract surgery with no astigmatism correction, either surgically or with a toric IOL (n = 100). Postoperative residual refractive astigmatism was the primary outcome.
Although he said that toric IOLs are the gold standard of astigmatism correction, Dr. Wörtz told Dr. Singh he wanted to see for himself whether it was worth treating astigmatism <1.00 D. “I feel we pretty definitively proved it is,” he asserted.
In the study, the FLACS group’s mean absolute postoperative astigmatism was 0.26±0.28 D compared to 0.43±0.4 D for the conventional group (P < .001), and more patients in the FLACS group (89%) had postoperative astigmatism <0.50 D compared to the standard cataract surgery group (71%; P = .001). Furthermore, a greater percentage of the FLACS patients (62%) achieved a UCDVA of 20/20 or better than the traditional-surgery group (48%) (P = .025). As Dr. Wörtz told Dr. Singh: “We found a statistically significant benefit of better uncorrected vision, about a 1.8 times higher chance of 20/20 vision by correcting those lower amounts of astigmatism.”
The main benefit of conducting this study, said Dr. Wörtz, was now having hard data to show his patients that correcting their astigmatism, even at small amounts, will give them a better quality of vision. “The genesis for this study was for me to be able to have a conversation with a patient and say, ‘I‘ve done the research. We’ve shown that this actually makes an improvement in your vision.’”
1. Wörtz G, Gupta PK, Goernert P, et al. Outcomes of femtosecond laser arcuate incisions in the treatment of low corneal astigmatism. Clin Ophthalmol. 2020;14:2229-2236.
