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Match problem with action to correct toric IOL misalignment
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Refractive error due to toric IOL misalignment can be addressed if the problem is matched with the appropriate corrective action, according to one surgeon.
Toric IOL misalignment has dramatic effects on vision. Rotation of 3° decreases cylinder correction by 10%, 10° by 35% and with 30°, the axis of residual cylinder is rotated to a new axis, usually oblique. Results may be worse than preoperatively even with the same magnitude of cylinder correction.
Misalignment may sometimes be caused by incorrect IOL placement at the time of surgery, occasionally by preoperative miscalculation, but it mostly occurs due to spontaneous rotation shortly after implantation, Kevin M. Miller, MD, said in a presentation at Hawaiian Eye 2017.
Postoperative rotation may be due to lens design issues, such as slippery materials or haptics that are too small for the capsular bag or to capsular bag issues. The capsular bag equator is often elliptical rather than circular and the haptics tend to seek out the longer axis, he said.
Other issues may be related to the surgery itself. With retained viscoelastics or leaky incisions, the vitreous can push the lens forward and rotate it. Finally, there is the small pupil.
“With a small pupil, you won’t be able to see the toric alignment marks on the lens, so you will do all sorts of tricks and cumbersome maneuvers and may end up leaving the lens off axis,” Miller said.
Toric IOL repositioning is “super easy,” he said. Although it is usually done within the first 6 months after surgery, it could also be effectively carried out after 1 year or more, if the appropriate technique is used.
“I mark the axis where the lens should be, and then I like to fully viscodissect the bag. A lot of people prefer to rotate a lens with minimum dissection, but I like to break all the capsular adhesions because I don’t want the lens to be nudged over and snap back to its original misaligned position, and I don’t want it to decenter because I failed to break adhesions. I spin the lens in the bag, break all the capsular adhesions and then I land it on the axis where I want it to be,” Miller said.
Using this technique, he has never had to reposition a toric lens a second time.
When spherical equivalent refractive error is high, IOL exchange is required. Miller suggested two ways of exchanging toric lenses.
“My favorite technique, which I use with acrylic lenses, is to refold them in the eye and take them out in one piece. Then I reform the bag, polish the capsule once again to clean it up and finally implant the new lens, making sure that it goes in on axis by checking it against the hash marks,” he said.
Other lenses cannot be folded out and need cutting. This is the case for the first version of the STAAR toric, which had an “uncanny” ability to find the long axis of the capsular bag, he said.
“In such cases, I cut the IOL lengthwise in two pieces, pull them out, go back, remove the fibrosis and put a replacement toric lens in,” Miller said.
A capsular tension ring may be inserted before the new lens is implanted to prevent asymmetric contractions, particularly in large eyes, he recommended.
If the patient is so far out from cataract surgery that IOL repositioning might be difficult, there are other strategies.
“I reposition and exchange lenses almost every week. I don’t find that it’s difficult even a couple of years later, but some people may not be comfortable with it,” Miller said.
If this is the case, when the spherical equivalent refractive error is within 0.5 D of the target, limbal relaxing incisions might be a good, less invasive and easier approach. – by Michela Cimberle
- Reference:
- VIDEO: Dealing with toric intraocular lens misalignment. https://www.healio.com/news/ophthalmology/20170127/video-dealing-with-toric-intraocular-lens-misalignment.
- For more information:
- Kevin M. Miller, MD, can be reached at UCLA Stein Eye Institute, 300 Stein Plaza, 2nd Floor, Los Angeles, CA 90095; email: kmiller@ucla.edu.
Disclosure: Miller reports he is a consultant to J&J Vision and Alcon.