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Steven Dewey, MD, shares his experience with a recent patient case when a lens rotated. A possibility for why this may have happened is the lens was not stable in the bag.
By Steven Dewey, MD, Special to Ophthalmology Times
Steven Dewey, MDColorado Springs, CO-A few months ago, I performed femtosecond laser-assisted cataract surgery on the left eye of a 67-year-old female patient, and implanted a toric lens (SN6AT9, Alcon Laboratories). Surgery was uneventful and the IOL was nicely aligned at the close of the case.
On the second day, the patient had a spike in IOP. I tapped the sideport incision to relieve pressure and placed the patient on brimonidine tartrate/timolol maleate (Combigan, Allergan) twice a day.
A few days later, closing in on the 1-week mark, she complained of blur. Ray tracing showed the IOL had rotated 69Ë counterclockwise (Figure 1).
Her refraction was now +2.75 -8.34 x 33. I wanted to give the capsular bag a chance to contract so we waited another 2 weeks to reposition the lens. At that point, the lens was easily rotated back into position and was perfectly aligned when I closed the eye, just as it had been at the initial surgery. This time I put the patient on Combigan and oral Diamox for 1 week as a preventive measure and she did not have an IOP spike.
However, she returned 2 weeks later with the same symptoms of blur: The lens had rotated out of position a second time, clockwise again, but this time only 44Ë. This time, partly due to the patient’s schedule, we waited another 2 months for the repositioning. I found the lens was still surprisingly mobile in the bag, with less fibrosis than expected.
I re-aligned the lens as before, but this time, tucked the nasal capsule under the IOL and then tucked the temporal capsule under the lens for a reverse optic capture (Figure 2).
Her vision improved to J1 at near with a -2.75 + 0.75 x 070 refraction. This (fortunately) very understanding patient was quite satisfied with the final result, and her lens has remained perfectly positioned ever since. In fact, 3 weeks after the second repositioning, we proceeded with toric lens surgery on her right eye, with no further rotational issues.
Looking for reasons
Video Part 1 of 3
Every degree of malrotation of a toric IOL results in a loss of efficacy of the cylinder correction.1 In a high-cylinder power lens like this one, a significant rotation can be disastrous. Not only is the cylinder not adequately corrected, but malrotation can actually result in compound imagery that cannot be fully corrected with spectacles.
Looking back at this case, it is difficult to say for certain why the lens rotated. The leading possibility is that the lens was not stable in the bag.
This patient had a relatively long axial length at 25.79 mm and larger white-to-white measurement at 12.72 mm, which point to an unusually large capsular bag. This certainly provides a larger theoretical space for IOL rotation, particularly in the absence of the usual rapid fibrosis. It could be that tapping the sideport incision encouraged lens movement.
However, this was done only once and the lens rotated twice. On the first repositioning, perhaps I was not as aggressive about opening the capsule as I might have been. Timing may have played a factor as well, as a slightly longer wait for the first corrective rotation may have allowed the capsule to contract further.
What I do know is that I’m glad this was a femtosecond laser procedure. This case reinforced that I have no desire to perform toric lens implantation without the laser, for both alignment and centration reasons.
Video Part 2 of 3
Re-aligning this toric lens was easier thanks to the intrastromal marks now made with the laser to identify the axis of astigmatism. Those marks were still visible during the repositioning surgeries (Figure 2).
I was also grateful for the precision of the capsulotomy, which was a perfectly round 4.7-mm opening in this case. Although I have confidence in my manual capsulorrhexis surgical skill, the accuracy required for aligning a high-powered toric lens is definitely facilitated by a perfect capsular opening.
Finally, I would not have felt as comfortable attempting the reverse optic capture that I ultimately performed in this eye with a manual capsulorrhexis.
The ability of the femtosecond laser (Catalys, Abbott Medical Optics) to center the capsulotomy on the scanned capsule is a huge benefit in toric or multifocal cases. We know that the pupil dilates asymmetrically and that the pupil center can therefore be different intraoperatively than it was preoperatively.
Furthermore, the pupil center does not always correlate with the center of the capsule where the lens will sit, which can mean that a capsular opening centered on the pupil will not have good overlap of the lens optic for the full 360Ë.
Video Part 3 of 3
In a retrospective analysis, William Wiley, MD, showed that the scanned capsule centration method resulted in more symmetric and complete overlap of the lens optic,2 which helps to ensure proper positioning of the lens.
Ray tracing (iTrace Workstation, Hoya Surgical Optics) has also proven to be a valuable surgical tool. In this case, I used it to guide my repositioning.
In another case of blurred vision 1 week after a toric lens implantation, ray tracing showed the lens was well aligned, so the lens was not repositioned. Instead the symptoms were resolved by treating the ocular surface.
Preoperative ray tracing is now obtained on every refractive cataract patient and is considered an essential element in planning an astigmatic correction. I average the ray tracing and Lenstar (Haag-Streit) measurements for the magnitude and axis of astigmatism.
Postoperatively, ray tracing is done only if the result was not optimal and I’m trying to understand why and determine how to fix the problem.
Accurate selection and alignment of toric IOLs is important to obtain optimal outcomes for astigmatic patients. Surgeons are fortunate to have new tools like ray tracing and femtosecond laser that make toric IOL surgery more predictable and increase the chance of superb outcomes.
2. Wiley WF, Bafna S, Jones J. Optical coherence tomography guided capsule bag-centered femtosecond laser capsulotomy. ASCRS, 2013.
Steven Dewey, MD
Dr. Dewey is head of the Colorado Springs Eye Clinic, Colorado Springs. Dr. Dewey is a consultant to Abbott Medical Optics and receives royalties from MST.