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Sir,

We report a case in which progressive anterior capsular fibrosis associated with a plate haptic silicone intraocular lens led to zonular disinsertion and dislocation of the capsular bag and implant 5 years after uncomplicated surgery. It is proposed that the same mechanism that leads to capsular phimosis may go on to cause late zonular disinsertion even up to 5 years after intraocular lens implantation.

Case report

A 76 year old gentleman with severe retinitis pigmentosa had undergone left sided cataract surgery 5 years previously with in-the-bag implantation of a plate haptic silicone intraocular lens (IOL) (C11UB, Chiron Vision Corporation, Claremont, CA, USA). There were no intraoperative complications and recovery was uneventful with corrected visual acuity of 6/9 in the operated eye. There was no pre-operative evidence of pseudoexfoliation or other clinical suspicion of zonular instability, nor history of blunt trauma to the eye, either pre or postoperatively.

The fellow eye had been operated upon 2 years after. There was no clinical suspicion of zonular instability noted preoperatively. Surgery was complicated by an intraoperative anterior capsule tear, which led to the implantation of a rigid polymethylmethacrylate IOL (MC550, Chiron Vision Corporation, Claremont, CA, USA). Laser posterior capsulotomy was performed 5 months after initial surgery due to posterior capsule opacification.

Mild phacodonesis and posterior capsule opacification were noted in the left eye 4 years after surgery, however capsulotomy was deferred as the visual axis was clear with corrected acuity of 6/18. During the 2 months prior to re-presentation, the patient had noticed that the vision in his left eye had become increasingly foggy. Visual acuity in the affected eye was hand movements improving to 6/24 with pinhole, and slit lamp examination showed marked iridodonesis. There was extensive capsular fibrosis with disinsertion of the superior zonules. The IOL implant within the capsular bag was seen hanging by a few inferior zonular fibres alone (Figure 1). The anterior vitreous face appeared intact with no evidence of vitreous prolapse.

Figure 1
figure 1

Inferiorly displaced plate haptic lens implant, attached only by a few inferior zonules.

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At subsequent surgery, the dislocated lens implant within the capsular bag was grasped through the pupil plane using utrata forceps and removed via a 5 mm corneal section. (Figure 2). No vitreous loss occurred and a 15 dioptre anterior chamber lens (MTA4U0, Alcon Laboratories, Fort Worth, TX, USA) was implanted. The patient made a good recovery from surgery with corrected acuity of 6/12 3 weeks postoperatively.

Figure 2
figure 2

Removal of primary implant via corneal incision.

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Comment

Posterior dislocation of plate haptic silicone IOLs in the immediate postoperative period and up to 26 months following Nd:YAG capsulotomy is well recognised. 1, 2, 3, 4, 5

There is minimal adherence between silicone IOLs and the surrounding capsular tissues when compared to lenses of other biomaterials.6 Capsular fibrosis due to fibrous metaplasia of residual lens epithelial cells is seen to occur with silicone IOLs.7, 8 This generates a centripetal force constricting the anterior capsular aperture. Progressive fibrosis of the anterior capsular rim leads to tension on the zonule insertion.

Cochener et al.9 prospectively evaluated the progressive contraction of the anterior capsular opening in a series of PMMA and three-piece silicone IOLs. They reported a significantly higher rate of contraction with the silicone cohort. This led them to suggest that silicone IOL implantation should be avoided in those eyes at risk from contraction of the capsulorhexis.

We believe the case described to be unique with progressive anterior capsular fibrosis causing disinsertion of the zonule 5 years after implantation of a plate haptic silicone IOL. It highlights an unusual complication of progressive anterior capsular fibrosis over a 5 year period, despite no evidence suggestive of zonular weakness prior to cataract surgery, no history of trauma and the absence of Nd:YAG capsulotomy. It may therefore be prudent to take caution with the implantation of plate haptic silicone IOLs in eyes with evidence of zonular instability or those conditions with which zonular weakness is associated.