Surgeon gives pearls on how to address residual refractive error after toric IOL implantation

Issue: May 10, 2017

Residual refractive error following the implantation of toric IOLs requires a methodic approach, careful evaluation and well-calibrated choice within a range of possible options, according to one surgeon.

“This surgery is a commitment but overall yields great satisfaction even if patients might be initially unhappy,” Elizabeth Yeu, MD, said at Hawaiian Eye 2017.

Overall, toric IOL patients are going to do well, but surprises may occasionally occur, she said. The first cause might be miscalculation, often due to incorrect estimation of posterior corneal astigmatism.

“Advanced online calculators, such as the Barrett toric calculator available on the ASCRS website, are of great help in identifying total corneal power,” Yeu said.

Dry eye, pterygium and corneal dystrophies such as epithelial basement membrane dystrophy may be overlooked and mistaken for refractive astigmatism, with disappointing postoperative outcomes.

Another common cause is IOL misalignment. In very long or short eyes, effective lens position may be difficult to predict, leading to over- or undercorrection. Incorrect identification of the steep axis intraoperatively or postoperative IOL rotation may lead to axis misalignment and decrease or even total loss of the corrective effect.

Prevention is key

Accurate preoperative evaluation is key in preventing these errors, Yeu said.

“First, we want these patients off all their postoperative drops and aggressively treat the ocular surface whether or not they have dry eye disease. Biometry, topography and OCT to rule out macular pathologies should be performed,” she said.

Careful ocular surface examination should also try to seek out other corneal surface abnormalities. Fluorescein staining, positive and negative, is mandatory “because irregularities can be very subtle and just looking without staining can be deceiving. What looks like astigmatism may in fact be dry eye and when treated it can change your outcome, so prevention is key,” Yeu said.

LRI and IOL rotation

Residual mixed astigmatism with spherical equivalent close to plano and a low amount of cylinder may require a limbal relaxing incision (LRI), performed manually or with a femtosecond laser.

When there is undercorrection and a previous LRI, the surgeon can lengthen it or add a second incision more centrally within the same meridian. Conversely, overcorrection with a flipped axis can potentially be treated with a LRI in the opposite axis. However, this is likely to compromise quality of vision, and other options should be considered, especially when the magnitude of the deviation is high, Yeu said.

When astigmatism is greater than 1 D,it may be necessary to evaluate if IOL realignment is warranted. Online tools such as www.astigmatismfix.com can help identify whether rotating the IOL would decrease residual astigmatism and calculate the amount of IOL rotation.

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After accurate identification and marking of the new meridian, Yeu performs a superior and inferior paracentesis and creates a good viscodissection of the capsular bag.

“Make sure you are not too aggressive and decompress occasionally. I like to inject the viscoelastic between the haptic-optic junction to release any of the fibrotic bands and then rotate the lens into position. It is important to remove the visco well from behind the toric IOL to prevent any further rotation. Finally, before coming out of the eye, tap down on the lens to make sure there is contact with the posterior capsule,” she said.

Laser vision correction and IOL exchange

If the spherical equivalent is also “off,” the decision might be between LRI or laser vision correction. This is going to depend on the tolerance of residual spherical equivalent, and a trial frame or a soft contact lens can be helpful in the interim. If laser vision correction is the choice, “timing is everything,” Yeu said.

“You want to wait at least 2 to 3 months after cataract surgery for the wounds and LRIs to settle, and you want to perform posterior capsulotomy before laser vision correction. One in 30 of my patients has refractive error changes after capsulotomy, especially when it’s an effective lens position that is creating some of that error,” she said.

IOL exchange might become necessary when quality of vision is poor due to IOL-related issues. With the many multifocal toric options coming into play for presbyopia correction, patients may have decreased quality of vision alongside the refractive error.

“There are several other reasons that might make IOL exchange the only option. Residual astigmatism and/or the spherical equivalent may be too high, something like 1.25 D or more. You may find out that realigning the IOL would not help. And you may not have laser vision correction as an option because the patient is not a good candidate due to dry eye disease or other characteristics of the cornea,” Yeu said.

In summary, when dealing with residual refractive error, “use a methodical approach,” she said. “Find the cause and treat it if possible, choosing between the various options, from the least invasive to IOL exchange.” – by Michela Cimberle

Reference:
VIDEO: Post toric intraocular lens surprises: Rotate, enhance or exchange it. http://www.healio.com/ophthalmology/cataract-surgery/news/online/%7B2763ac64-26ef-48ba-8a22-c313f261737a%7D/video-post-toric-intraocular-lens-surprises-rotate-enhance-or-exchange-it.

For more information:
Elizabeth Yeu, MD, can be reached at Virginia Eye Consultants, 241 Corporate Blvd., Suite 210, Norfolk, VA 23502; email: eyeu@vec2020.com.

Disclosure: Yeu reports she is on the speakers bureaus of Abbott Medical Optics, Alcon, Allergan, Bio-Tissue, Ocular Therapeutix, Omeros, Shire and TearLab; has ownership interest in Modernizing Medicine, RPS and Strathspey Crown; and is on the advisory boards of Abbott Medical Optics, Alcon, Allergan, ArcScan, Bausch + Lomb/Valeant, Bio-Tissue, Eyekon E.R.D., i-Optics, Kala Pharmaceuticals, Ocular Therapeutix, Ocusoft, TearLab and TearScience.