New technologies allow surgeons to target lower astigmatism thresholds
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Even small amounts of astigmatism reduce patients’ postoperative quality of uncorrected vision and satisfaction after refractive cataract surgery.
Refractive cataract surgery patients have high expectations of their surgical outcomes. They live more active lives than previous generations in this age group and expect to reduce their dependence on glasses while meeting the demands of their lifestyles.
New technologies are fine-tuning astigmatism correction, helping surgeons achieve better visual quality than ever before.
Advancing capabilities
Most recently, our objective for postoperative astigmatism was less than 1 D, but our targets continue to shrink, with most cataract surgeons currently aiming for 0.5 D of astigmatism or less. We are learning that we can do even better, approaching 0.25 D or even 0 D of astigmatism. We have already achieved this goal with spectacles and refractive corneal surgery and hope to attain the same outcomes in our patients having refractive cataract surgery.
Advances in refraction, keratometry and corneal topography enable us to obtain accurate preoperative measurements. Most refractive cataract surgeons use biometers that provide an accurate magnitude and improved axis, such as the Lensar system, IOLMaster 700 (Zeiss) and Lenstar (Haag-Streit). We also have technology that offers better corneal topography, such as the Pentacam (Oculus), Galilei (Ziemer), Cassini, iTrace (Tracey Technologies) and Atlas (Zeiss). Combining multiple technologies increases accuracy.
However, the primary challenge in correcting astigmatism is precise alignment of the incision or toric IOL on the correct meridian. Technologies that enable more exact placement are taking us to the next level in reducing astigmatism.
Manual alignment marks on the cornea tend to range from 3° to 5° in size and may be prone to errors resulting from ink diffusion or other sources. We need to be within 2° or 3° of our target. Each degree of misalignment reduces astigmatism correction of the toric IOL by 3.3%, and new astigmatism may be induced on a different axis.
With Lensar technology, which provides iris-guided registration and IntelliAxis capsular marks, we can align the toric IOL or place the incision more precisely on the meridian of astigmatism to produce better outcomes.
I moderated a panel at the American Society of Cataract and Refractive Surgery meeting in which several papers showed impressive outcomes down to 0.25 D of astigmatism. Numerous conference papers have shown that the Lensar system effectively assists surgeons in aligning toric IOLs.
Refractive cataract surgeons often discuss the merits of femtosecond laser-assisted cataract surgery (FLACS) vs. classical manual phacoemulsification. FLACS seems to be capable of making a measurable improvement in setting the appropriate magnitude and meridian of astigmatic correction.
Targeting a smaller degree of astigmatism increases the number of patients to whom we can offer this opportunity. Aiming for 0.75 D of astigmatism expands our potential population to 30%, 0.5 D to 50%, and 0.25 D to 70%. We can explain to patients that even 0.25 D of astigmatism matters, and we would like them to achieve the best quality vision that they can by correcting it.
Patient satisfaction
Data demonstrate that patient satisfaction depends on our ability to correct astigmatism and produce high-quality visual acuity, especially in patients who hope to reduce their dependence on spectacles. If a patient is paying a premium fee for advanced-technology IOLs to reduce their dependence on glasses, it is critical that we correct their astigmatism to produce optimal outcomes.
Satisfying patients and referring doctors helps us generate a manageable and sustainable practice and grows our practices. At Minnesota Eye Consultants, approximately 50% of our surgical patients are referred by optometrists, who expect high-quality visual outcomes after our procedures. Many of our cases also come from patient referrals.
We can now achieve high-quality uncorrected vision and improve patient satisfaction by implementing the femtosecond laser to better align toric IOLs and incisions and correct astigmatism.
- References:
- Bauer NJ, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2008.05.031.
- Motwani M. Clin Ophthalmol. 2017;doi:10.2147/OPTH.S133840.
- Schallhorn SC, et al. J Cataract Refract Surg. 2021;doi:10.1097/j.jcrs.0000000000000560.
- Visco D, et al. Safety and effectiveness of a novel femtosecond laser-assisted capsular marking system for the alignment of toric IOLs: A prospective study. Presented at: European Society of Cataract and Refractive Surgeons meeting; Sept. 14-18, 2019; Paris.
- For more information:
- Richard L. Lindstrom, MD, of Minnesota Eye Consultants, can be reached at rllindstrom@mneye.com.
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