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Cataract Surgery | Feb 2013

Strategies for Correction of IOL Power Surprises

Surgeons share their preferred protocols.

ALESSANDRO FRANCHINI, MD

Despite many great advances in surgical techniques, IOL materials and designs, biometry, and IOL power calculation formulas, patients can still be left with significant residual refractive errors after cataract surgery. We have three methods for correcting unexpected refractive errors in cataract surgery—IOL exchange, piggyback IOL implantation, and laser refractive surgery—and it is our job to choose the most appropriate solution according to the amount and type of refractive error and the time between the two surgeries. When we treat these patients, it is important to remember that tolerance of minor refractive errors has decreased with the widespread use of premium IOLs, specifically toric and multifocal lenses.

In patients with up to 1.00 D of residual hyperopia, I resolve the refractive error simply by tweaking the optic capture. Using a cannula, the optic is moved in front of the capsulorrhexis into the iris plane. This maneuver is easy, especially if the lens is a three-piece design. If the residual refractive error is between 1.00 D and 3.00 D of hyperopia or a limited myopic or astigmatic error, I prefer to correct the defect with corneal laser refractive surgery. In my opinion, LASIK is safe when performed at least 3 months after cataract surgery, as complications related to wound healing and IOL stability are very rare after this time. For more than 3.00 D of hyperopia, myopia up to 8.00 D, or astigmatism up to 5.00 D, secondary IOL implantation is an excellent option. I implant the Sulcoflex (Rayner Intraocular Lenses Ltd.) in these cases. The surgery is easy, and the smaller incision that can be used to implant these thin IOLs reduces the risk of capsular break.

An alternative for any amount of residual intraocular error is IOL exchange. This option is my preferred method for high residual errors when no more than 1 month has elapsed after cataract surgery. Some surgeons cut the lens in the anterior chamber before removing it; instead, I fold the lens to avoid further manipulations that can damage the capsule. I first try to free the proximal haptic by breaking any adherences with an ophthalmic viscosurgical device (OVD) and a cyclodialysis spatula. Once the optic has been removed from the bag and placed in the iris plane, I proceed to free the distal haptic. After refilling the capsular bag with OVD to keep away the posterior capsule, I am ready to fold the lens in the eye. To do this, I introduce a spatula through a paracentesis opposite the main incision (Figure 1). Next, using folding forceps, I push and fold the optic on the spatula (Figure 2) and remove the lens though the unenlarged main incision (Figure 3).

If too much time has passed after cataract surgery and the proximal or distal haptics are shrink-wrapped tightly to the capsular bag, I cut the haptics, remove only the optic, and then implant a new lens in the sulcus.

In my opinion, lens-based procedures are preferable for treating large postoperative surprises. IOL exchange is my first option if the correction is required soon after cataract surgery, whereas Sulcoflex implantation is preferred if the correction is required several months later. On the other hand, LASIK performed 3 months postoperatively appears to be safe and more effective and predictable to reduce cylinder than IOL exchange. Furthermore, refractive laser procedures are indicated in eyes with questionable capsular integrity (Table 1).

Alessandro Franchini, MD, is a Professor at the School of Ophthalmological Specialization, University of Florence, Italy. Dr. Franchini states that he has no financial interest in the companies or products mentioned. He may be reached at e-mail: alessandrofranchini@yahoo.it.

RUPERT MENAPACE, MD, FEBO

With modern biometry and IOL power calculation formulas, refractive surprises have become rare. One remaining cause for higher errors, however, is erroneous IOL power selection. With multifocal IOLs, even small deviations from emmetropia may require surgical intervention. With standard IOLs, deviation from the target refraction usually is detected between 1 week and 1 month after surgery, when postoperative refraction is often determined for the first time. With premium IOLs, discovery usually occurs after 1 week.

Because modern acrylic IOL materials usually induce only moderate fibrosis and are easy to cut, the IOL may still be easily viscodissected from the fused capsular leaves and the optic cut in half with capsular scissors as long as 4 to 6 weeks after implantation. My primary approach to residual errors, therefore, is lens exchange under topical anesthesia.

Using a spatula, I reopen my temporal posterior limbal incision after reincising the covering conjunctiva if necessary. Lidocaine 1% is injected, and aqueous is exchanged for a high-viscosity OVD. Two paracenteses are reopened or made again, and through these a blunt spatula or cannula is introduced to detect the proper place to begin viscodissection. Through the main incision, a bent or angulated microcannula is inserted, and viscodissection is performed while superfluous OVD is allowed to escape. Subincisional dissection may require insertion through one of the paracenteses. Using two spatulas, the IOL is then rotated to relocate the haptics into the anterior chamber and orient the IOL axis horizontally (Figure 4). The temporal haptic is then externalized through the main incision (Figure 5).

Generous OVD is reinstilled above and beneath the IOL to create ample spaces between the lens, posterior capsule, and corneal endothelium. My standard 2.2-mm incision is then extended to about 3.0 mm internally and 2.6 mm externally. As a right-handed surgeon, I insert a chopper through the left paracentesis to subsequently grasp and hold the nasal optic edge under the haptic junction (to prevent the optic from being pushed nasally and tilted) while cutting it in half with capsular scissors (Figure 6). This is always easily achieved. After the first half of the IOL is extracted by pulling on the already externalized haptic, the second half is removed directly or after rotating it 180° and again externalizing the haptic (Figure 7). Then the capsular bag equator is fully dissected and expanded again using a high-viscosity OVD. With the capsular bag reformed, an IOL of the correct power is then implanted (Figure 8).

When a longer time has passed after surgery, I assess capsular fibrosis with the pupil fully dilated. In the past, when IOL exchange was the only option, capsular reopening was successful in almost all cases—even with the pronounced fibrotic reaction triggered by silicone IOLs. If not, cutting the haptic at the junction and removing the optic while leaving one or both haptics in place is still a good option.

If I expect a difficult IOL or optic removal, I resort to one of two alternative techniques: implantation of a supplementary lens such as the Add-on IOL (HumanOptics AG or Rayner Intraocular Lenses Ltd.) or corneal laser correction. As a prerequisite for the first option, the iris-to-optic distance at the pupillary margin, as judged under oblique slit-beam illumination, must be sufficient. If this space is too small, I resort to laser correction to avoid the risk of pigment dispersion caused by constant optic-iris chafe and pupillary block. An iridectomy will exclude the latter, but it will intensify the contact between the iris and IOL, and thus the risk of chronic lens-iris chafe, which may cause low-grade chronic subclinical inflammation.

The long-term risk profile of Add-on IOLs is still undetermined, and the precision of correcting small refractive errors, including residual astigmatism, is much higher with corneal surface laser ablation. Therefore, with larger refractive errors, I prefer IOL exchange whenever possible, and with smaller errors, particularly with multifocal IOLs, I resort to corneal surface laser ablation after the refraction has fully stabilized.

Rupert Menapace, MD, FEBO, is a Professor and Head of the Intraocular Lens Service and Outpatient Ophthalmic Surgery Unit in the Department of Ophthalmology, Medical University of Vienna, Vienna General Hospital. Professor Menapace states that he no financial interest in the products or companies mentioned. He may be reached at tel: +43 1 40400 7931; e-mail: rupert.menapace@ meduniwien.ac.at.

PIERRE-JEAN PISELLA, MD, PhD

My strategy for correcting a refractive surprise after an IOL power calculation error depends on the amount of residual refractive error. Typically, I choose between IOL exchange and a laser corneal ablation procedure, mainly PRK or LASIK.

If the eye has a large residual refractive error, which I consider anything more than 3.00 D, I opt for IOL exchange if it is an early finding just after the postoperative period. However, if it is a smaller amount, a late finding, or it is not easy for the patient to return to the hospital, I prefer a corneal refractive procedure. In these cases, I select either PRK or LASIK depending on the patient’s corneal profile. I do not prefer a customized profile either in PRK or LASIK, and I select a standard procedure, except in rare cases with high amounts of residual astigmatism.

In a typical year, I do approximately 10 surface ablation enhancement procedures in patients with residual refractive errors after IOL power calculation errors, with very nice results. In my experience, patients who opted for a multifocal IOL are more likely to have bothersome residual refractive errors. In some cases, a refractive surprise of 0.50 D is enough to warrant correction with surface ablation in these patients. I always propose a simple PRK, performing it 1 to 3 months postoperatively, after the refraction is stable.

I prefer surface ablation to IOL exchange because there are not as many additional risks. After IOL explantation, the capsular bag may not be stable, and I may not be able to exchange the IOL for the same model. This is especially true with premium lens implants. If I need to use a monofocal IOL, it can present a problem for the majority of premium IOL patients, who tend to have high expectations.

Another reason I rarely perform IOL exchange is because of the associated cost to the patient. Whereas a secondary laser touch-up is included in the base price for a premium IOL, exchanging the IOL is not. Piggyback IOL implantation is also a solution, but I do not have personal experience with this technique.

Pierre-Jean Pisella, MD, PhD, is a Professor at the School of Medicine, University of Tours, and Chairman of the Department of Ophthalmology at Hôpital Bretonneau, in Tours, France. Dr. Pisella states that he has no financial interest in the material presented in the article. He may be reached at tel: +33 247474733; fax: +33 247478136; e-mail: pj.pisella@chu-tours.fr.

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