Intraocular lens (IOL) movement is an uncommon complication of Nd:YAG laser capsulotomy.1 The incidence of this complication using modern lenses and methods of laser capsulotomy is not yet documented.1 A large proportion of the reports available described delayed dislocation of posterior chamber IOLs occurring only after completion of the procedure.2–7 Only a single study reported an inadvertent IOL fracture and immediate dislocation of lens fragments into the anterior chamber during Nd:YAG laser capsulotomy.8 To our knowledge, this case is the first to describe Nd:YAG capsulotomy performed on an eye with congenital glaucoma, which was complicated by immediate IOL subluxation that happened during the procedure.
An 18-year-old woman was being managed as a case of bilateral primary congenital glaucoma. This patient already had Ahmed valve implantation of the right eye and trabeculectomy of the left eye 3 years before her latest consult. Trabeculectomy was performed on the right eye 3 months after the drainage device implantation. In the course of follow-up, needling with 5-fluorouracil was performed 5 times on the right eye. An Ahmed valve was also eventually implanted on the left eye due to failure to control intraocular pressure (IOP). She developed bilateral cataracts within 2 years of her first ocular surgery, for which she underwent irrigation and aspiration of the lens with posterior chamber IOL implantation. Single-piece acrylic IOLs (right eye, Aurofold, Aurolab; left eye Acrysof SA60AT, Alcon) were placed in the posterior chambers of both eyes. Needling with 5-fluorouracil injection was also performed on the right eye on the same sitting. Postoperative corrected distance visual acuities (CDVA) of the right eye and left eye were 6/30 and 6/60, respectively. She was maintained on topical ocular hypotensive agents for a persistently elevated IOP despite having had multiple procedures for glaucoma. Refraction was regularly performed to ensure best correction of vision. On regular follow-up, her CDVA remained at 6/30 for the right eye and 6/60 for the left eye; however, she began complaining of cloudiness of vision for both eyes. Slitlamp examination revealed visually significant posterior capsular opacities on both eyes, with the opacity being thicker on the right eye. Retinoscopy streaks were also diminished. The plan was to perform Nd:YAG laser capsulotomy to remove the opacities blocking the visual axis.
An ocular examination was performed before the procedure. Corneal diameters were measured to be 13.5 mm (horizontal) and 13.0 mm (vertical) for both eyes. The corneas were clear. The glaucoma drainage devices were placed superotemporally, whereas the flattened trabeculectomy sites were seen superonasally for both eyes. The anterior chambers were deep and quiet. The drainage tubes were positioned anterior to the iris plane, having no contact with the iris or the cornea. On slitlamp examination of the dilated eyes, no portion of the anterior capsule was seen in front of the IOLs, signifying that the lenses were positioned in the sulcus for both eyes. The slight inferior displacement of the IOLs was attributed to the small size of the IOL relative to the enlarged sulcus in the presence of buphthalmos. Review of records showed that the capsular bag was intact. There was no preoperative and intraoperative suspicion of zonulysis. The placement of the single-piece IOL into the sulcus instead of the bag may have resulted from various factors, which may include inadvertent anterior injection of the IOL, presence of a large anterior capsulorhexis, aggressive intraoperative fluidics, inadequate viscosurgical and cortical cleanup, or elevated vitreous pressure. Both eyes exhibited posterior capsular opacification. No clinical signs of zonular weakness and IOL instability were appreciated before the planned Nd:YAG capsulotomy. Both optic nerves were cupped out. The preprocedure IOP was 6 mm Hg for the right eye and 8 mm Hg for the left eye.
The decision was made to proceed with Nd:YAG capsulotomy of the right eye. Laser shots with power of 1.0 to 2.0 mJ were administered at the 8 o'clock position up to the 4 o'clock positions in a circular pattern behind the lens optic. When shots were being administered at the 4 o'clock position, the IOL subluxated inferiorly, and the procedure was immediately terminated. A total of 59 shots corresponding to a total power of 114 mJ were administered. Figure 1 shows the inferiorly subluxated IOL on the right eye.
The visual acuity of the right eye decreased to 6/60. The IOP was 21 mm Hg, and the IOL appeared to be unstable in its subluxated position. The patient had IOL explantation, posterior capsulectomy, anterior vitrectomy, and iris-claw lens implantation of the right eye. The visual acuity returned to 6/30 after the procedure. The patient decided to defer plans of undergoing Nd:YAG capsulotomy on the left eye.
The stability of an IOL implant is determined by the degree of capsular fibrosis and the integrity of the zonules. Capsular contraction has been identified in the literature as a cause of IOL dislocation after Nd:YAG laser capsulotomy.1,2,5 Capsulotomy size and IOL material also affect the risk for IOL dislocation after laser capsulotomy.1,2,4,7 Initially, lens dislocation was observed more frequently in plate-haptic silicone lens; this was attributed to the decreased fibrosis of the lens capsules and contraction of the capsular rim with this type of IOL.2,4,7 Nearly all published reports described delayed movement of the IOL, occurring a few days up to several months after Nd:YAG laser capsulotomy.2–6 Only a single report mentioned immediate dislocation of the IOL during Nd:YAG capsulotomy, although this was associated with fragmentation of the lens due to the laser.8 In this case report, the IOL subluxated inferiorly immediately after laser shots were administered in a circular pattern along the superior 8 o'clock hours of the capsule behind the lens optic.
Gupta et al. used ultrasound biomicroscopy to examine eyes with primary congenital glaucoma. The degree of zonular stretching was found to be correlated with axial length and not with corneal diameters. Zonular lengthening was thought to result from traction from an enlarged globe diameter and a nonenlarged lens. Consequently, the lens was seen to be more mobile in these patients.9 For this case, ultrasound biomicroscopy done after the attempted laser procedure revealed stretched zonular fibers on the left eye and undetectable the inferior zonular fibers on the right eye as shown in Figure 2. The finding on the right eye was reflective of a lack of inferior zonular tension. The patient may have had inherent zonular weakness as a result of the buphthalmos and multiple ocular procedures performed previously. The placement of the single-piece IOL, instead of a 3-piece IOL, into the sulcus may have also resulted in disruption of the zonular fibers. The zonulysis may have developed only after fibrosis of the zonular fibers; thus, the patient did not present with superior displacement of the capsular bag before the Nd:YAG capsulotomy. It is hypothesized that the IOL was held stable only by its adhesions to the central portion of the capsule. Its rapid dislocation during the procedure was indicative of an unstable and inadequate adhesion between the periphery of the lens optic, the lens haptics, and the capsule. This could have been due to the prolonged use of topical steroids and antifibrotic agents in an eye that underwent multiple ocular procedures. The disruption of the adhesion between the lens optic and the capsule caused the IOL to fall inferiorly where the sulcus was no longer intact.
To our knowledge, this report is the first to describe a complicated Nd:YAG laser capsulotomy in an eye with congenital glaucoma that has undergone multiple surgeries. A careful evaluation is warranted to determine the accurate position and configuration of the IOL, the condition of the zonules, and the integrity of the sulcus before performing even a simple procedure such as Nd:YAG laser capsulotomy. Ultrasound biomicroscopy may reveal important information that may contribute to decision making when dealing with patients with conditions such as congenital glaucoma. If Nd:YAG capsulotomy will be performed on this subset of patients, the ophthalmologist must decrease the risk for subluxation by using low power settings and by creation of a small, central capsulotomy. Patients should be advised regarding the risks of the procedure, and it should be performed with great caution. Lastly, this report also emphasizes the importance of proper IOL selection and positioning to decrease the risk for long-term complications.
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