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Cataract Surgery | Jul 2011

Refractive Surprises and IOL Dislocation

No surgeon enjoys dealing with complications after cataract surgery, but they must be resolved quickly and efficiently to keep today’s demanding patients happy. To ensure that a small surgical hurdle does not progress to a traumatic situation, we have established protocols for some of the most frequent complications. In some cases, this includes identifying at-risk patients prior to surgery.1

REFRACTIVE SURPRISES

One complication that can transpire after cataract surgery is the refractive surprise—a common occurrence in patients who have previously undergone refractive surgery, but also not restricted to this population.

Surprises triggered by previous refractive surgery. Post- PRK patients are tricky because their preoperative refraction and keratometry (K) readings cannot always be obtained from the referring ophthalmic center. We have tried to determine the proper lens power using online calculation formulas; however, the results of these are often unpredictable. For instance, we recently operated on a 46-yearold patient with nuclear cataracts and high myopia; in the first eye, axial length was 31.5 mm, mean K reading (post-PRK) was 34.50 D, and the refraction was -10.00 D prior to cataract surgery. The IOL power calculation suggested a lens power of 10.00 D, but immediately after surgery the patient’s refraction was 6.00 D. We therefore exchanged the IOL for a lens with a power of 17.00 D. Immediately after this second surgery, the refraction was 0.50 D spherical equivalent. One month later, we operated on the contralateral eye, which had an axial length of 31.75 mm and a mean K reading of 35.00 D. We chose a lens power of 16.00 D, expecting to achieve the target refraction. However, the refraction was -3.00 D, and we therefore exchanged the IOL for a 13.00 D lens. With this adjustment, the postoperative refraction improved to 0.75 D spherical equivalent.

Our protocol for post-PRK patients includes the following:

  • Keeping an open line of communication with the patient, explaining that IOL power is less predictable due to the previous refractive procedure;
  • Avoiding overfilling the anterior chamber;
  • Implanting an IOL that can be easily explanted;
  • Performing the incision on the steep meridian; and
  • Calculating the refraction with an autorefractometer immediately after surgery.

If lens exchange is necessary, we enlarge the incision to 4 mm, fold or cut the old lens as needed, and remove it from the eye. We use an acrylic hydrophilic or hydrophobic one-piece IOL and replace the IOL within 1 or 2 hours.1 In some cases, if we are using a dedicated microincision IOL, the lens can be explanted through a 2.2-mm incision (Figure 1).

IOL-related refractive surprises. In today’s era of microincision cataract surgery (MICS), lens designs can trigger refractive surprises. To pass through a 1.8- to 2- mm incision, the IOL must be made of soft and malleable materials; however, IOLs made of these materials are not as stable in the capsular bag as more rigid IOLs, and the lens may therefore become decentered. Additionally, the normal contraction of the capsular bag after surgery can be problematic, as forward and backward movements of the lens (especially higher-power lenses) change the postoperative refraction. When we started performing MICS in 2002, we immediately observed that, with higher-power IOLs (28.00 to 30.00 D), postoperative refraction could change by as much as 2.00 or 3.00 D of myopia or hyperopia, depending on the forward or backward movement of the IOL.1 Fortunately, current MICS lens designs have improved, and stability within the capsular bag is no longer a major concern.2

Surprises in aphakic eyes. In eyes with a compromised endothelium, we like to perform Descemet stripping automated endothelial keratoplasty (DSAEK) after cataract surgery, and this can lead to another type of IOL surprise. We typically perform the procedures in two surgical episodes, implanting a scleral- or iris-fixated IOL in the first surgery and DSAEK in the second, ending with injection of an air bubble to promote attachment of the thin endothelial flap graft. If the air bubble dislocates in the vitreous cavity, an air-pupillary block can be created. In an aphakic eye, this can be relieved with gentle pressure on the iris. However, if an iris-fixated IOL was implanted we must take care so that it remains enclaved.

In a recent case, the iris-fixated IOL became disenclaved during this maneuver.3 It was necessary to convert from DSAEK to a posterior vitrectomy to retrieve the IOL. With a 25-gauge transconjunctival trocar, we injected DK-Line perfluorocarbon liquid (Bausch + Lomb, Rochester, New York) under the IOL until it was possible to grasp the IOL with vitreoretinal forceps. The IOL was relocated over the iris, the pupil was constricted with acetylcholine chloride, and the IOL was fixated under the iris. Vitrectomy concluded with DK-Line removal. DSAEK was performed 1 week later.

IOL DISLOCATION

IOL dislocation is a common problem after cataract surgery. Causes include capsular bag dislocation due to pseudoexfoliation syndrome or high myopia or insufficient posterior capsular support. Whenever possible, we manage these problems with minimally invasive methods, such as refixating the IOL in the capsular bag, fixating one haptic loop in the sclera, or fixating the IOL to the sclera.

If the entire IOL has dislocated into the vitreous, we prepare two scleral flaps to fixate the IOL to the sclera. We perform 23-gauge sutureless transconjunctival vitrectomy, aiming for complete vitrectomy to avoid any vitreoretinal traction, and inject DK-Line (Figure 2) under the IOL to support and levitate it. When the IOL has been elevated close to the pupillary zone, we pass a polypropylene suture under the first loop (Figure 3).

A 25-gauge needle is introduced through one of the scleral flaps, the suture is inserted into the barrel of the needle, and the needle is withdrawn from the eye, bringing the suture with it (Figure 4). A knot is created under the scleral flap, and the IOL loop is fixated to the sclera. This procedure is similar to a previously described suturing technique.4 This minimally invasive technique does not require IOL exchange.

CONCLUSION

Refractive surprises and IOL dislocation are common complications after cataract surgery. There is not a rigid protocol to address these types of complications, and therefore the surgeon must devise techniques that he or she is comfortable with. Keep in mind that every eye is different, but in most cases the problem can be solved with a little surgical creativity.

Simonetta Morselli, MD, is Chief of the Ophthalmic Unit, San Bassiano Hospital, Bassano del Grappa, Italy. Dr. Morselli is a member of the CRST Europe Editorial Board. Dr. Morselli states that she is a consultant to Bausch + Lomb International. She may be reached at e-mail: simonetta.morselli@gmail.com.

Antonio Toso, MD, is a Consultant and Vitreoretinal Specialist, Ophthalmic Unit, San Bassiano Hospital, Bassano del Grappa, Italy. Dr. Toso states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: antonio.toso@gmail.com.

  1. McCartney PJ.Refractive surprise after piggyback intraocular lens implantation.J Cataract Refract Surg. 2011;37(7):1372-1373.
  2. Can I,Takmaz T,Bayhan HA,Bostanc› Ceran B.Aspheric microincision intraocular lens implantation with biaxial microincision cataract surgery:efficacy and reliability.J Cataract Refract Surg.2010;36(11):1905-1911.
  3. Ma DJ,Choi HJ,Kim MK,Wee WR.Clinical comparison of ciliary sulcus and pars plana locations for posterior chamber intraocular lens transscleral fixation. J Cataract Refract Surg.2011 Jun 23.[Epub ahead of print.]
  4. Kyoung Tak Ma,MD,Sung Yong Kang,MD et al Modified Siepser sliding knot technique for scleral fixation of subluxated posterior chamber intraocular lens. J Cataract Refract Surg.2010;36(1):6-8.

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