From diagnostic devices to phaco machines to IOLs—technological improvements are helping surgeons deliver superior outcomes to patients. Despite these advances, the myth that correcting low levels of astigmatism during cataract surgery is unnecessary persists. This article discusses why addressing even minimal astigmatism is essential for achieving optimal visual results.
PREOPERATIVE CONSIDERATIONS AND SURGICAL PRECISION
Before cataract surgery, a refraction is performed to optimize the patient’s BCVA with glasses, contact lenses, or refractive surgery. During the preoperative evaluation, biometry is performed, and ocular surface disease must be managed to ensure reliable measurements. Intraoperatively, surgeons’ attention to detail and optimization of all controllable factors facilitate excellent surgical results.
Astigmatism is one such factor. Even a low amount of residual astigmatism can significantly affect a patient’s UCVA and quality of life, especially when they are executing tasks requiring precision, such as reading or driving at night. In this article, less than 1.00 D of astigmatism is classified as low, 1.00 to 2.00 D as moderate, and greater than 2.00 D as high.
Data indicate that 47.4% of patients have between 0.00 and 0.75 D of corneal astigmatism before cataract surgery and 62.2% have between 0.00 and 1.00 D.1 Many patients who present to an ophthalmology practice therefore have low astigmatism.1
THE IMPACT OF RESIDUAL ASTIGMATISM
Patients’ Visual Acuity and Level of Satisfaction
Research has demonstrated that even minimal residual astigmatism (eg, 0.50 D) decreases patients’ visual acuity and can leave them dissatisfied after cataract surgery. Studies have shown that patients with uncorrected astigmatism are less satisfied with their visual quality than those whose astigmatism was corrected during cataract surgery.2 With advances in surgical techniques and IOL technology, most patients expect excellent postoperative vision. Uncorrected astigmatism often leads to residual refractive errors that may require correction with glasses or contact lenses.3
Technological Advances in IOLs
The introduction of toric IOLs has revolutionized cataract surgery by providing an effective means of correcting astigmatism. Studies have shown that toric IOLs not only improve patients’ visual outcomes but also reduce their postoperative reliance on corrective eyewear, even among patients with low amounts of astigmatism.
WHY CORRECTING LOW ASTIGMATISM IS NECESSARY
Enhanced Surgical Precision
Femtosecond lasers and improved IOL calculation formulas have increased the precision of cataract surgery. These and other innovations improve measurement accuracy and facilitate the correction of even low levels of astigmatism, thereby reducing the risk of residual refractive errors. By addressing low astigmatism, surgeons can fully leverage modern technologies to deliver the best possible visual outcomes.
Cost-Effectiveness and Long-Term Benefits
Although toric IOLs and limbal relaxing incisions may involve a higher up-front cost compared to standard monofocal IOLs, the long-term benefits often justify the investment. Patients whose astigmatism is corrected are less likely to need postoperative corrective measures, the cost of which can accumulate over time. Additionally, improved visual outcomes enhance patients’ independence and quality of life, potentially reducing their need for further medical intervention.
Consistency in Surgical Outcomes
Correcting astigmatism during cataract surgery leads to more consistent and predictable visual outcomes. These enhance patient satisfaction and their confidence in the surgical process. A meta-analysis published in the British Journal of Ophthalmology found that patients whose astigmatism was corrected during surgery reported significantly higher satisfaction and better overall visual quality compared to those with uncorrected astigmatism.4
WAYS TO CORRECT LOW LEVELS OF ASTIGMATISM
Technological advances have provided surgeons with multiple options for correcting low levels of astigmatism. A key factor in addressing low astigmatism is surgeons’ improved understanding of the optical system, including the role of posterior corneal astigmatism, which has led to more accurate IOL calculation formulas.
Astigmatism-Correcting IOLs
Astigmatism-correcting IOLs, including toric IOLs and the Light Adjustable Lens (RxSight), are among the most common methods used to correct astigmatism. These lenses are highly accurate and can be utilized by all cataract surgeons. Modern IOL calculation formulas now recommend toric IOLs for low levels of anterior corneal astigmatism. With the Light Adjustable Lens, surgeons can fine-tune even small amounts of astigmatism postoperatively.
Corneal Relaxing Incisions
Corneal relaxing incisions, including limbal relaxing and arcuate incisions, offer a precise way to correct low amounts of astigmatism. Various nomograms are available to aid with determining the most appropriate treatment for each patient.
Excimer Laser Refinements
Excimer laser procedures such as LASIK can be performed to address residual astigmatism after cataract surgery. The accuracy and predictability of LASIK in pseudophakic patients are comparable to those in younger phakic patients.
DEBUNKING THE MYTH
The belief that correcting low levels of astigmatism in cataract patients is unnecessary is not supported by current evidence or expert opinion. Correcting even minimal astigmatism during cataract surgery is essential for optimizing patients’ visual acuity, improving their satisfaction, and maximizing the benefits of modern surgical technologies. A comprehensive approach to cataract surgery that addresses all refractive errors to provide patients with the best possible vision and quality of life is crucial.
1. Hill W. Astigmatism correction. East Valley Ophthalmology. Accessed September 11, 2024. https://doctor-hill.com/mesa-eye-doctors/specialists/cataract-surgery/astigmatism-correction
2. Schallhorn SC, Hettinger KA, Pelouskova M, et al. Effect of residual astigmatism on uncorrected visual acuity and patient satisfaction in pseudophakic patients. J Cataract Refract Surg. 2021;47(8):991-998.
3. Wu C. Control of astigmatism in cataract patients. American Academy of Ophthalmology. May 7, 2008. Accessed September 11, 2024. https://www.aao.org/education/current-insight/control-of-astigmatism-in-cataract-patients
4. Yen WT, Weng TH, Lin TY, Tai MC, Chen YH, Chang YM. Femtosecond laser-assisted astigmatic keratotomy versus toric IOL implantation for correcting astigmatism in cataract patients: a systematic review and meta-analysis with trial sequential analysis. Br J Ophthalmol. Published online April 4, 2024. doi:10.1136/bjo-2024-325195
