About 90% of patients in my practice choose the lifestyle benefits of multifocal, accommodating or toric IOLs and/or femtosecond laser-assisted cataract surgery. Central to the promise we make in offering lifestyle lenses is the provision of high-quality uncorrected visual acuity, and that means correcting astigmatism is essential.
Leaving presbyopic IOL patients with residual astigmatism — even seemingly minor amounts of 0.5 D to 0.75 D — can severely affect a patient’s vision and make him or her unhappy. Astigmatism degrades visual quality, particularly with multifocal optics, and can result in patient dissatisfaction with the outcome of an otherwise excellent surgery.
A. James Khodabakhsh
It is not difficult for cataract surgeons to treat astigmatism at the time of surgery, particularly with the addition of femtosecond lasers to our armamentarium. I determine what treatment approach to take based on the preoperative keratometry. I like to compare multiple measures of corneal astigmatism, including manual keratometry readings, autorefractor keratometry readings, IOLMaster (Carl Zeiss Meditec) and Lenstar (Haag-Streit). Topography and corneal OCT are also part of my premium IOL package.
At the most basic level, it is important to perfect your entry wound incisions to ensure that they are as atraumatic and astigmatically neutral as possible. I make a 2.2- to 2.4-mm incision and like to use a lens platform that can be injected through that incision regardless of dioptric power. The injector should fit easily or with wound assist through the incision, so that you do not need to enlarge the wound and potentially induce unpredictable amounts of cylinder.
Making on-axis incisions is a good start to correcting astigmatism, but this approach can correct only a small amount. The next step in the hierarchy of astigmatism correction would be limbal relaxing incisions (LRIs). Even with peripheral pachymetry, LRIs can be unpredictable. In the past, often my preference was to perform laser vision correction approximately 8 to 12 weeks after IOL implantation instead. However, this is less convenient for the patient because it involves two procedures and a delay in achieving the final visual outcome.
My approach has changed significantly since I acquired the Catalys femtosecond laser (Abbott Medical Optics). Astigmatic keratotomy (AK) incisions with the laser are far more repeatable and predictable than I found LRIs to be in the past, so I now rely on them extensively. Consequently, I have been able to reduce my rate of laser vision correction enhancement after presbyopic IOL implantation from about 15% to 5%.
I typically make paired, symmetrical, anterior penetrating incisions and open them at the time of surgery, but the laser gives me the flexibility to make asymmetrical cuts or to titrate the correction by opening an incision later.
I use a modified version of the Donnenfeld conventional LRI nomogram for femtosecond laser AKs. When I first started performing laser incisions, I began conservatively at 60% of the Donnenfeld nomogram but found this was undercorrecting. In eyes that have with-the-rule (WTR) astigmatism, there is usually less corneal astigmatism than we are measuring due to the contribution of posterior corneal astigmatism, so I move the optical zone out to 9.4 mm and make the incisions at 75% of the length of the Donnenfeld conventional LRI nomogram. In eyes with against-the-rule (ATR) astigmatism, I use a more aggressive treatment, at 85% of the conventional LRI nomogram at an optical zone of 9.1 mm.
My ceiling for laser AKs also depends on the location of the astigmatism. I will correct up to 2 D of WTR astigmatism and up to about 1.5 D of ATR astigmatism with AKs. I turn to toric IOLs for astigmatism beyond that range or consider laser vision correction if the patient still wants a multifocal IOL.
Even with improvements in incisional correction and great toric IOL options, there is no getting around the fact that a minority of patients will need LASIK or PRK enhancement. As a premium IOL surgeon, if you are not prepared to perform laser vision correction yourself, you should partner with a refractive surgeon to handle those cases for you and be upfront about additional charges if enhancement is not included in your global fees.
I now use the Catalys femtosecond laser in almost every presbyopia-correcting IOL case, even if there is as little as 0.5 D to 1 D of astigmatism. I have seen many cases as second-opinion consults in which the patient is unhappy and posting negative feedback online about his or her original surgeon simply because of residual astigmatism. Taking the initiative to manage astigmatism proactively with on-axis incisions, manual LRIs, laser AKs or laser vision correction is the key to satisfying your presbyopic lifestyle lens patients.
For more information:
A. James Khodabakhsh, MD, can be reached at Beverly Hills Institute of Ophthalmology, 416 N. Bedford Drive #300, Beverly Hills, CA 90210; email: email@example.com
Disclosure: Khodabakhsh reports he is a consultant and speaker for Bausch + Lomb and AMO and owns OptiMedica and LenSx lasers.