In their series of 9 pseudoexfoliation patients with spontaneous capsular bag/IOL dislocations, Jehan and coauthors1 highlight the surprising delay in the onset of this complication—5 to 10 years postoperatively. This raises the concern that additional patients will have dislocations even later because of continued, progressive zonular weakening. The younger the patient, the more the risk of this late complication should be considered.
The delay in onset makes it difficult to determine the true incidence of this complication. An informal survey taken during a course on complications showed that nearly 20% of the audience (approximately 60 surgeons) had seen this complication personally (M. Kraff, MD, “Clinical Decisions in the Management of Complications of Cataract and IOL Surgery,” presented at the American Academy of Ophthalmology annual meeting, New Orleans, Louisiana, USA, November 2001). Most had seen it in eyes with silicone IOLs, and only a minority had seen it with acrylic IOLs.
The primary causative factors are open to speculation. Possibilities include patient factors, operative factors, capsulorhexis size, and the IOL design and material. The rarity of crystalline lens subluxation with pseudoexfoliation suggests that progressive, age-related zonular weakening alone is not responsible. If intraoperative zonular damage were the primary factor, one would expect the dislocation to occur much sooner. That this complication has not occurred with can-opener capsulotomies suggests that a capsulorhexis and bag fixation are prerequisites. Capsulorhexis fibrosis and shrinkage would presumably exert centripetal traction on the zonules.
Finally, what about IOL-related factors? The 9 published cases included 8 poly(methyl methacrylate) (PMMA) IOLs and 1 plate-haptic silicone IOL. However, 2 of my patients with a 3-piece SI-40 silicone IOL (Allergan) had spontaneous dislocation 3 1/2 and 5 years postoperatively. In these 2 cases, the capsulorhexis had contracted to a diameter of 3.0 mm and 3.5 mm. What is unclear is whether the capsulorhexis contraction weakened the zonules or whether preexisting zonular weakness allowed the shrinkage to occur.2–4 In other words, was capsulorhexis contraction the cause or the effect?
Based on these observations, I would make 3 recommendations for a younger pseudoexfoliation patient.
- I would choose a 3-piece, 6.0 mm acrylic IOL with PMMA haptics such as the AcrySof® (Alcon) or Sensar® (Allergan). Hydrophobic acrylic material is associated with less anterior capsule fibrosis and contraction than silicone, PMMA, and hydrogel materials.5–7 Jehan and coauthors1 theorize that a capsular tension ring (CTR) might reduce zonular tension from bag contracture. Until such devices are approved by the U.S. Food and Drug Administration (FDA), selecting rigid haptics with maximally broad capsular contact might be advisable. Compared with the single-piece, flexible acrylic haptic, the longer PMMA haptics are more likely exert centrifugal tension on the capsular fornices.
- Although a capsulorhexis slightly overlapping the optic diameter helps prevent posterior capsule opacification (PCO), I would avoid too small a diameter. This might require secondarily enlarging the capsulorhexis after IOL insertion by incising and retearing it.
- I recommend checking the capsulorhexis diameter 1 to 2 months postoperatively. If the capsulorhexis is already constricting or becoming fibrotic, relaxing “sphincterotomies” to the edge could be performed with a neodymium:YAG (Nd:YAG) laser.8 This would prevent vision-impairing capsulophimosis and might mitigate progressive zonular traction from further capsulorhexis contraction.
1. Jehan FS, Mamalis N, Crandall AS. Spontaneous late dislocation of intraocular lens within the capsular bag in pseudoexfoliation patients. Ophthalmology 2001; 108:1727-1731
2. Hansen SO, Crandall AS, Olson RJ. Progressive constriction of the anterior capsular opening following intact capsulorhexis. J Cataract Refract Surg 1993; 19:77-82
3. Davison JA. Capsule contraction syndrome. J Cataract Refract Surg 1993; 19:582-589
4. Hayashi H, Hayashi K, Nakao F, Hayashi F. Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation syndrome. Br J Ophthalmol 1998; 82:1429-1432
5. Hayashi K, Hayashi H, Nakao F, Hayashi F, et al. Reduction in the area of the anterior capsule opening after polymethylmethacrylate, silicone, and soft acrylic intraocular lens implantation. Am J Ophthalmol 1997; 123:441-447
6. Werner L, Pandey SK, Apple DJ, et al. Anterior capsule opacification. Ophthalmology 2001; 108:1675-1681
7. Hayashi K, Hayashi H, Nakao F, Hayashi F. Anterior capsule contraction and intraocular lens decentration and tilt after hydrogel lens implantation. Br J Ophthalmol 2001; 85:1294-1297
8. Kimura W, Yamanishi S, Kimura T, et al. Measuring the anterior capsule opening after cataract surgery to assess capsule shrinkage. J Cataract Refract Surg 1998; 24:1235-1238