Posterior capsule opacification (PCO) is a common but easily treatable complication after cataract surgery. Posterior capsulotomy with the neodymium:YAG (Nd:YAG) laser usually results in complete resolution of this complication. However, there have been reports of proliferation of the lens epithelial remnants after Nd:YAG laser capsulotomy that caused significant visual impairment and required secondary laser intervention.1–4 We report a case of secondary closure of the posterior capsulotomy opening because of lens epithelial cell (LEC) proliferation. The diagnosis was complicated by severe glistenings in the acrylic foldable intraocular lens (IOL). Explantation of the IOL was considered based on the glistenings.
A 67-year-old man who had cataract surgery in the right eye 2 years earlier and an Nd:YAG laser capsulotomy 1 year earlier was referred to us because of decreased vision. He had had phacoemulsification and implantation of an acrylic foldable IOL (AcrySof®, MA60BM, Alcon). The surgery was reported to be uneventful, but the IOL was implanted upside down. Visual acuity improved from 20/125 preoperatively to 20/16 postoperatively. The patient had non-insulin-dependent diabetes mellitus without retinopathy. One year later, PCO developed and the visual acuity decreased to 20/200. An Nd:YAG laser posterior capsulotomy was performed, and the visual acuity recovered to 20/16.
Six months after laser treatment, the visual acuity in the right eye again gradually deteriorated to 20/200. Since the posterior capsulotomy window appeared to be open but the retinal view was obscured, vitreous opacity was suspected. There was background diabetic retinopathy, but the macular region appeared intact on ophthalmoscopic examination and fluorescein angiography. Treatment with an oral nonsteroidal antiinflammatory agent was initiated but was ineffective. The visual acuity declined to 20/300. Based on consultation with a retina specialist, vitreous opacity and IOL clouding from glistenings were suspected. The patient was referred to our department for possible explantation of the IOL and vitrectomy.
Upon examination, marked glistenings were seen within the optic of the IOL (Figure 1) and linear cracks were seen peripherally. The margin of the posterior capsulotomy opening was clear, but the area in which the posterior capsule was absent was covered by proliferated material (Figure 2). The fundus view was hazy; it was not possible to confirm the presence or absence of vitreous opacity.
The Nd:YAG laser was used to remove the proliferated material behind the IOL. The material closely adhered to the posterior surface of the IOL but was easily removed by laser irradiation of approximately 1.0 mJ. The opacity was successfully removed (Figure 3) and the primary capsulotomy window slightly enlarged. After capsulotomy, the patient's visual acuity returned to 20/16. The retinal view fully cleared. During the 2-year follow-up after the second laser intervention, there was no recurrence of the posterior capsulotomy closure.
After Nd:YAG laser posterior capsulotomy, the residual LECs may proliferate along the capsulotomy margin, forming a string of pearls on the vitreous side of the posterior capsule and the IOL.1,4 The development of a dense and extensive string of pearls will decrease visual acuity or lead to disabling glare. There have been a few reports of secondary Nd:YAG laser intervention for the treatment of proliferated lens epithelial remnants.1–4 To our knowledge, however, total closure of an Nd:YAG laser capsulotomy opening has not been documented. After a posterior continuous curvilinear capsulorhexis (PCCC), total secondary closure of the opening has been reported.5,6 In the case of PCCC closure, it was speculated that cells grow over the anterior hyaloid membrane.5 At the time of the Nd:YAG laser capsulotomy in our patient, we confirmed that cellular proliferations were located on the posterior IOL surface. Residual LECs should be able to proliferate and migrate on scaffolds other than the capsules.
Jones and coauthors3 observed massive proliferation of lens epithelial remnants in 8 eyes in patients who had preexisting retinal pathology. Tassignon and coauthors6 found a high frequency of PCCC reclosure in eyes with increased risk for postoperative inflammation. Although this is speculative, the presence of diabetic retinopathy in this patient might have contributed to the development of the complication. The blood-aqueous barrier function is known to be compromised in diabetic patients.7–9 Thus, the increased level of growth factors, such as basic fibroblast and insulin-like growth factors, in these predisposed eyes might play a role in the proliferation and differentiation of LECs. When the posterior capsule is disrupted by the Nd:YAG laser, intravitreal growth factors can affect LECs directly. Although the aqueous humor may dilute these factors and diminish their activities, an IOL implanted in the capsular bag divides the anterior chamber and the vitreous cavity, hindering the dilution of these factors.4 Masket1 found that string of pearls develops only when a continuous curvilinear capsulorhexis (CCC) was performed in the initial cataract surgery. Kato et al.4 demonstrate that a string of pearls is seen predominantly in eyes with CCC and IOL implantation. In addition, tight adhesion of the acrylic foldable IOL to the capsular bag10,11 could have contributed to the compartmentalization, enhancing the regrowth of LECs behind the IOL.
Without knowing the possibility of secondary closure of a posterior capsulotomy opening, diagnosing the complication in this case was difficult. Moreover, the coexistence of marked glistenings in the acrylic foldable IOL complicated the diagnosis. In fact, vitreous opacity and IOL clouding because of glistenings were suspected, and explantation of the IOL and vitrectomy were considered. If IOL exchange surgery had been performed, the visual acuity should have improved because of the removal of LECs with the IOL optic, suggesting the IOL as the cause of the visual impairment. Although the effect of glistenings in acrylic foldable IOLs on the visual function of patients is controversial,12–15 the presence of marked glistenings was evidently not the cause of the reduced vision in our patient.
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