Toric IOL alignment achieves higher levels of success
New technologies have improved rotational stability and marking capability.
In the era of modern-day premium cataract surgery, I wonder how 1,386,254.5 D of astigmatism were left uncorrected last year, and that same trend remains this year. Warren Hill and others have repeatedly reported that between 70% and 90% of patients have treatable astigmatism, with the majority still untreated. So the question remains: Why are premium surgeons not treating more astigmatism at the time of cataract surgery? Is it inconsistent outcomes, are astigmatic incisions an art, is toric IOL alignment not precise, is it time-consuming intraoperatively and perioperatively, is it a lack of confidence and/or the fear of having to be a salesman as astigmatism management is a noncovered part of cataract surgery?
What we do know and what I want to focus on in this month’s Premium Channel column is outcomes with toric IOLs, specifically how they have evolved with great success based on improved IOL technology in terms of rotational stability and improved marking capability to place the IOL at the correct steep axis that is determined preoperatively based on improved diagnostics that account for posterior corneal astigmatism.
Precise alignment of a toric IOL is not an option but rather a must-have. We know that for every 1° of toric IOL misalignment, there is a loss of 3.3% of astigmatism correction, or a 10° misalignment ending in about 33% loss of astigmatic effect. Ink markings, although simple to do, are imprecise, can run and can rinse away just when they are needed at the time of IOL placement. Ink marks can also be so large that they cover 5° of coverage alone. Corneal scratch marks are laborious and can end up in painful small corneal abrasions in the early postoperative period for patients. Surgical tricks utilized in the past, as I presented at the American Society of Cataract and Refractive Surgery meeting about 10 years ago, include an ink mark technique utilizing the superior and inferior rectus muscle insertions (in patients without prior strabismus surgery) as landmarks as the globe will always rotate back in upright position to these landmarks. Other great marking tools have evolved, such as axis markers that can be used intraoperatively and more advanced hand-held devices such as the RoboMarker (Surgilum), which help eliminate parallax errors for the surgeon and keep the marks visible under the femtosecond laser for astigmatic incisions in longer duration until the toric IOL is placed with fewer run-off issues.
The technology with which I am most excited about and what I have most experience with is the Lensar femtosecond laser system with Streamline IntelliAxis-C and IntelliAxis-L technology (Lensar) for improved toric IOL alignment. Many papers, especially on the latter, were recently presented at the ASCRS meeting in San Diego. Both methods work by preoperative upright topographic imaging performed in the office using Pentacam (Oculus), Cassini (i-Optics) and/or OPD III (Marco/Nidek) devices. These images via iris registration adjust for any cyclorotation errors intraoperatively when the patient is in the supine position under the femtosecond laser. IntelliAxis-C creates 5° marks in the cornea in the steep axis 180° apart, which are superficial without any astigmatic effect themselves. These marks eliminate the need for ink marking and allow for placing the toric IOL in the correct steep axis planned preoperatively.
These marks, though, still can have parallax errors. IntelliAxis-L is where the steep axis marks for the toric IOL are part of a unique capsulotomy construction at the time of the Lensar procedure and aid in postoperative verification of alignment and even repositioning of a toric IOL if required in the immediate postoperative period. These capsular marks have been studied in an ex vivo porcine model looking at maximum tensile strength and force displacement patterns compared with the capsulotomies created without them, and there was no statistically significant difference between these groups, as presented at the 2018 European Society of Cataract and Refractive Surgeons meeting in Vienna. There were many papers on the topic at the recent ASCRS meeting, with outcomes showing frequency distribution of residual refractive cylinder at 1 month postoperatively ranging from 93.3% to 98% 0.5 D cylinder or less among the presenters using IntelliAxis-L technology.
In summary, toric IOL alignment has evolved significantly over the last 30 years I have been practicing cataract surgery, and I believe we are just at the beginning of even greater things to come with our premium IOLs.
- Holladay JT, et al. J Cataract Refract Surg. 2019;doi:10.1016/j.jcrs.2018.09.028.
- Jackson M. Tensile strength of a novel femtosecond laser capsulotomy with capsular nubs to guide toric IOL alignment. Presented at: European Society of Cataract and Refractive Surgeons meeting; Sept. 22-26, 2018; Vienna.
- Jackson M, et al. Toric IOL alignment: femtosecond laser-assisted capsular marks versus intrastromal corneal marks. Presented at: American Society of Cataract and Refractive Surgery annual meeting; May 3-7, 2019; San Diego.
- For more information:
- Mitchell A. Jackson, MD, can be reached at Jacksoneye, 300 N. Milwaukee Ave., Suite L, Lake Villa, IL 60046; email: email@example.com.
Disclosure: Jackson reports he is a consultant for Bausch + Lomb, Lensar, Oculus, Marco, i-Optics and Surgilum.