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Astigmatism management in cataract surgery: A review of available treatments

ByEdward J. Holland, MD

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As advancements in refractive cataract surgery continue, patients have come to expect excellent uncorrected visual acuity. In order to meet these high patient expectations, surgeons want a means of managing astigmatism that is safe, precise, accurate and convenient, and yields predictive outcomes.

Available options

Surgeons want a means of managing astigmatism that is safe, precise, accurate and convenient, and yields predictive outcomes. —Edward J. Holland, MD

Of available modalities for correcting astigmatism, spectacles are the most common. Contact lenses are often a preference for patients with high degrees of astigmatism or irregular astigmatism. A relaxing incision is the most common means of surgically treating astigmatism. Limbal-relaxing incisions (LRIs) are more popular among surgeons than paralimbal relaxing incisions or astigmatic keratotomy (AK) because an LRI is slightly easier to perform, with fewer surgical complications. Laser vision correction is also an available option, as is the implantation of a toric IOL.

According to a survey published in August 2006, approximately 56% of cataract patients have enough postoperative astigmatism to require spectacle correction.¹ Thus, astigmatism is common. LRIs, corneal-relaxing incisions (CRIs) or AK account for approximately 35% of surgical treatments for patients with cataracts and astigmatism (Figure).¹

Frequency of Surgical Treatments for Astigmatism Figure. Of surgical treatments, LRI, CRI or AK accounts for 34.6% of treatment of astigmatism in patients with cataracts.1

Relaxing incisions

LRIs, or peripheral CRIs, provide varying results. Douglas D. Koch, MD, and colleagues have developed a nomogram (Table), but each surgeon should adjust the nomogram based on personal clinical results.² The apparent complexity of such a nomogram, based on age and the amount of astigmatism, may be the reason many surgeons have not adopted the procedure. In addition, results are unpredictable, regression is common and the treatment range is limited. High degrees of astigmatism cannot be corrected using LRI, and LRI is contraindicated in patients with asymmetric astigmatism, such as a patient with superior keratoconus or thin peripheral cornea. Because an LRI adds two incisions in the cornea, both of which are larger than the original cataract incision, wound-healing complications can occur. Epithelial defects and an increased risk of stromal complications often occur in older patients or patients with ocular surface disease such as dry eye or blepharitis.

Toric IOLs

The first toric IOL approved by the Food and Drug Administration in the United States was manufactured by STAAR Surgical Company (Monrovia, Calif.) and corrected a significant amount of astigmatism; an issue existed, however, with the rotational stability of the IOL. Approximately 24% of patients involved in the FDA clinical trial had greater than 10° rotation; this required a second procedure such as a repositioning of the IOL or an IOL exchange in a number of patients.³ However, the IOL model used in the FDA clinical trial had a 10.8-mm diameter; STAAR also has a lens available with a diameter of 11.2 mm.

Table: Koch Nomogram The Koch nomogram provides a guide for LRI but should be adjusted based on personal clinical results.2

Laser vision correction

Laser vision correction is an accurate and safe means to manage corneal astigmatism. The typical patient with astigmatism and cataracts, however, will not elect to undergo this procedure because it must be done as an additional procedure to the cataract surgery. In addition, the cost of laser vision correction makes this option less appealing for most patients.

Conclusion

Although many modalities exist to correct astigmatism in a patient with cataracts, surgeons are still searching for a satisfactory treatment method that is accurate, safe and convenient, and that yields predictable outcomes comparable to a patient’s high expectations. Spectacles and contact lenses are safe and effective but may be inconvenient for patients. Laser vision correction is accurate and safe but may be inconvenient and costly for patients. Surgically, relaxing incisions provide varying results and an increased risk of complications, and, for toric IOLs to be safe, effective and convenient, rotational stability must be enduring.

References

1. Market Scope LLC. 2006 Comprehensive Report on the Global IOL Market. August 2006. Available at http://www427.pair.com/mktsc/reports/archive/2006/ 08/the_2005_comprehensive_report.html. Last accessed December 27, 2006.
2. Wang L, Misra M, Koch D. Peripheral corneal relaxing incisions combined with cataract surgery. J Cataract Refract Surg. 2003;29:712-722.
3. STAAR data. Summary of Safety and Effectiveness Data. PMA P880091/S14. Available at http://www.fda.gov/cdrh/pdf/p880091s014.pdf. Last accessed February 7, 2007.