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Speaker offers tips for implanting toric IOLs

Latest-generation toric IOLs give surgeons a more precise method for treating astigmatism.

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The AcrySof Toric IOL (Alcon Laboratories, Inc.) achieves significantly better astigmatism correction compared with astigmatic keratotomy and limbal relaxing incisions, according to Bonnie An Henderson, MD, who offered advice on patient selection, preoperative measurements and implantation techniques during her presentation at the 2009 meeting of the American Society of Cataract and Refractive Surgery.

“Everyone knows that this [AcrySof Toric IOL] has been a wonderful invention for the correction of astigmatism,” she said.

Dr. Henderson, an assistant clinical professor of ophthalmology at Harvard Medical School and partner at the Ophthalmic Consultants of Boston, noted that the AcrySof Toric IOL can correct astigmatism in patients with 0.75 D to >2.0 D of cylinder, but it is especially useful for patients who are not candidates for incisional surgery or for the small subset of patients who have opposing astigmatism in their lens vs. their cornea.

Bonnie An Henderson

Preoperative preparations

Preoperative measurements should be taken before administering eye drops, according to Dr. Henderson. Using an IOL Master (Carl Zeiss Meditec), surgeons can calculate IOL spherical power. Dr. Henderson suggested that surgeons optimize their A-constant for the AcrySof Toric IOL. To determine IOL power calculations online, Dr. Henderson referred surgeons to the AcrySof Toric Calculator at www.acrysoftoriccalculator.com. Surgeons are prompted to enter dioptric power and axis for both the steep and the flat axes, IOL spherical power, surgically induced astigmatism and incision location.

“One helpful tip is to hang the printout from the online IOL calculator on your microscope so that you can actually look at it while you are making the incision,” she said.

Another important part of the preoperative process is marking the astigmatic axis on the cornea, according to Dr. Henderson. When the IOL is aligned correctly, the patient has a better chance of attaining spectacle independence. When marking the eye manually, surgeons should make one 6-o’clock mark, she said. When using a commercial marker, surgeons should align the orientation marks with the steep axis. Marking the cornea properly ensures proper alignment and optimizes visual results.

This is important because the AcrySof Toric IOL rotated more than 10 degrees in 8% of patients, especially younger patients, in one study, even though the average potential rotation was approximately 4 degrees overall, Dr. Henderson said, citing a study published in the American Journal of Ophthalmology.¹

Overall, the rotational stability of the AcrySof Toric IOL has been found to be excellent. Several studies have shown that the AcrySof rotated less than 4 degrees.^2,3 Also, if the IOL were to rotate, this would usually occur in the first post-operative week.⁴

Polishing the capsule

Polishing the capsule is also important when using toric IOLs, according to Dr. Henderson.

“One final tip about the toric IOL is that when you polish the anterior and the posterior capsules, leave the areas where the haptics are placed unpolished.

IOL implantation and placement

Dr. Henderson emphasized the need for accurate preoperative measures, but also stressed the importance of IOL placement during surgery. When lenses are placed, they are rotated clockwise.

Once the IOL is in the eye, Dr. Henderson suggests waiting for it to unfold before extracting the viscoelastic to avoid IOL “bounce” that can occur if the haptics have not yet unfolded. Once the IOL has completely unfolded, surgeons should ensure that all viscoelastic is removed. She recommends using a cohesive viscoelastic because it is easier to extract at the end of surgery. Residual viscoelastic in the eye can cause the IOL to rotate. This rotation would occur within the first week after surgery and can be easily corrected in the office or the operating room, according to Dr. Henderson.

“Align [the IOL] properly with a Y hook or any lens manipulator. Then at the end of surgery, this is very important, … when you take off the drapes and remove the lid speculum, ... make sure the anterior chamber is properly formed and not collapsed,” Dr. Henderson said.

References:

1. Swami AU, Steinert RF, Osborne WE, White AA. Rotational malposition during laser in situ keratomileusis. Am J Ophthalmol. 2002;133:561-562.
2. Lane SS. The AcrySof Toric IOL’s FDA clinical trial results. Cataract & Refractive Surgery Today. May 2006;6:66-68.
3. Chang DF. Comparative rotational stability of single-piece open-loop acrylic and plate-haptic silicone toric intraocular lenses. J Cataract Refract Surg. 2008;34:1842-1847.
4. Till JS, Yoder PR Jr, Wilcox TK, Spielman JL. Toric intraocular lens implantation: 100 consecutive cases. J Cataract Refract Surg. 2002;28:295-301.