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Cover Focus | July/Aug '19

Approaching Astigmatism

The Benefits of Torics

Sumitra S. Khandelwal, MD

When it comes to managing astigmatism, toric IOLs truly nail it. Of course, one appeal of limbal relaxing incisions (LRIs) is the instant gratification that they provide. If done correctly, LRIs can yield good immediate postoperative results, especially for patients with low levels of astigmatism. But I’m a surgeon who appreciates a long-term outcome.

So, what advantages do toric IOLs have over other approaches to astigmatism management? In one prospective trial published in 2016,1 investigators compared three methods for correcting preexisting astigmatism during phacoemulsification: (1) LRIs on the steep meridian, (2) extension and suturing of the phaco incisions created at the steep meridian, and (3) toric IOL implantation. Postoperative distance UCVA improved in all three groups. The difference in postoperative distance UCVA was not statistically significant among the study groups throughout the initial follow-up. However, by week 24, UCVA was significantly better in the toric IOL group.

In another prospective study comparing toric IOLs and LRIs in patients with ≤ 3.00 D of astigmatism,2 the percentage of eyes in need of spectacles was lower in the toric IOL group than in the LRI group at postoperative months 1 and 3. More importantly, on vector analysis, the magnitude of error was negative in the LRI group, indicating undercorrection, whereas the magnitude of error was close to zero for the toric IOL group at postoperative months 1 and 3.

Toric IOLs are sometimes used in combination with LRIs for the management of higher amounts of astigmatism. In one study, investigators compared the use of high-cylinder toric IOLs with a combined approach of low-cylinder toric IOLs and LRIs.3 They found that higher-cylinder toric IOLs achieved better clinical outcomes, were more predictable, and had a longer effect. Postoperative corneal and ocular higher-order aberrations were also higher in the LRI group than in the toric IOL group.

There is certainly a place for LRIs to treat lower amounts of astigmatism. But until we can fully understand the cornea and control its tissue response, toric IOLs remain the more predictable treatment option for astigmatism management in my practice.

1. Mohammad-Rabei H, Mohammad-Rabei E, Espandar G, et al. Three methods for correction of astigmatism during phacoemulsification. J Ophthalmic Vis Res. 2016;11(2):162-167.

2. Lam DKT, Chow VSW, Ye C, Ng PKF. Comparative evaluation of aspheric toric intraocular lens implantation and limbal relaxing incisions in eyes with cataracts and ≤3 dioptres of astigmatism. Br J Ophthalmol. 2015;100(2).

3. Ouchi M. High-cylinder toric intraocular lens implantation versus combined surgery of low-cylinder intraocular lens implantation and limbal relaxing incision for high-astigmatism eyes. Clin Ophthalmol. 2014;8:661-667.

Sumitra S. Khandelwal, MD
  • Assistant Professor of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston
  • sumitra.khandelwal@bcm.edu
  • Financial disclosure: Alcon, Bausch + Lomb

A Case for Corneal Relaxing Incisions

Brandon D. Ayres, MD

Most patients undergoing cataract surgery have some level of astigmatism, of which up to 1.50 D is relatively correctable with corneal relaxing incisions. In the United States today, toric IOLs start at about 1.00 D of correction. Lower-power toric IOLs are not yet available to US surgeons. Therefore, we cannot adequately manage astigmatism without knowing how to create a corneal relaxing incision.

Nomograms are being developed and published to help surgeons determine the ideal length and location of their corneal relaxing incisions. Surgeons can also customize these nomograms to ensure greater uniformity and consistency of their individual results. Further, the stability of LRIs has been established, as studies have shown them remain stable for at least 3 years, which is the longest follow-up available so far.1

The creation of corneal relaxing incisions is an effective and necessary technique, but it does require attention to detail, experience, and the ability to analyze one’s data and develop a nomogram. Fortunately, this process has been greatly simplified by the femtosecond laser. Further, with corneal relaxing incisions, there is no argument over which platform is superior. A relaxing incision is a relaxing incision. They do work, and they are 100% rotationally stable.

There is little cost associated with corneal relaxing incisions. When we first get into medicine, we tend to think is all about treating patients. But as we get further into our careers, we realize it is about treating patients and about money. With even the most game-changing technologies, physicians will question the cost and potential reimbursement. With corneal relaxing incisions, there is no additional expense beyond the tool used for their creation, whether a diamond blade, sharp steel blade, or femtosecond laser.

Another advantage of corneal relaxing incisions is that they can be augmented at the slip lamp. If a patient comes in at postoperative month 1 or month 3 and some astigmatism is returning, the surgeon can simply take a diamond blade and titrate the incision. It is not necessary to take the patient back into the OR as it would be to rerotate or exchange an IOL.

Corneal relaxing incisions are typically considered for smaller amounts of astigmatism, but what about patients with high degrees of astigmatism or even irregular astigmatism? I have seen many patients with corneal transplants and 7.00, 8.00, or 9.00 D of astigmatism. Would you implant a toric IOL in a patient with a 13-year-old graft? What about when the patient needs another graft in 10 years but has a T9? What are you going to do with that lenticular cylinder? Using an arcuate incision is a nice way to address astigmatism in these patients.

Toric IOLs undoubtedly play a large role in astigmatism management and are a necessary tool for cataract surgeons, especially for treating patients with larger orders of astigmatism or negative astigmatism. But having some knowledge of and experience with corneal or limbal relaxing incisions is essential for managing astigmatism, especially in the lower powers.

1. Lim R, Borasio E, Ilari L. Long-term stability of keratometric astigmatism after limbal relaxing incisions. J Cataract Refract Surg. 2014;40:1676-1681.

Brandon D. Ayres, MD
  • Surgeon in the Cornea Service, Wills Eye Hospital, Philadelphia
  • brandonayres@mac.com
  • Financial disclosure: Consultant (Alcon)

July/Aug '19