A displaced IOL following phacoemulsification—varying from minimally to extremely dislocated into the vitreous—is an infrequent complication. The causes could be related to one or more of the following: technique/skill of the surgeon, characteristics of the implant, and anatomical and structural defects of the eye. Treatment most commonly consists of repositioning or replacing the faulty IOL. Additionally, many patients with mild subluxation could greatly benefit from conservative treatment with pilocarpine drops.
IOL SUBLUXATION
Dislocated IOLs are sometimes referred to as either sunset syndrome (ie, when the implant is inferiorly subluxated)1 or westeast syndrome (ie, if subluxated superiorly).2 Alternately, the implant may become displaced well into the vitreous, through defects in the capsular bag.3 The main risk factors include silicone plate-haptic IOLs,4 IOLs with a small optic diameter,5 an existing tear in the posterior capsule with inadequate vitrectomy, dehiscence of the zonule, scarring of the posterior capsule,6 and pseudoexfoliation.7 Depending on the severity of IOL displacement, patients may present with a variety of symptoms. These may include blurring of vision, halos, and double vision.
If the implant is grossly displaced, such as when the edge of the optic lies below the geometric pupil center or when the IOL is posteriorly dislocated, it must be repositioned or replaced to recover the disturbed visual function.8 Replacing an implant is not without a risk, however, particularly when the bag is disorganised and fibrosed. Such risks include jeapordizing the integrity of the capsular bag; damaging the iris, hyphema, or corneal endothelium; disturbing the vitreous; and subsequent macular edema and retinal detachment.9
There are several circumstances that indicate a more conservative approach to treating a dislocated IOL. Because the lifespan of our patients continues to increase, it is not uncommon for us to operate on people aged in their 80s to mid-90s. Such patients are likely to be suffering with other systemic illnesses and must be treated with care. Alternatively, conservative treatments are necessary for patients who are either unfit for surgery (eg, severe skeletal problems, advanced heart diseases) or adverse to undergoing further surgical procedures. Additionally, patients with only one functioning eye may be best treated with a more traditional measure to avoid the risk of surgical complications.
Pilocarpine can be very rewarding under these circumstances. It is worth noting, however, that this treatment will only work in mild-to-moderate cases of displacement. Furthermore, the nearest edge of the optics must be a fair distance away from the geometric pupil center.
Pilocarpine increases the depth of focus via its miotic effect, and more importantly, it removes the aphakic refractive element of the displaced implant.
Some ophthalmologists do not like the idea of using pilocarpine in the eye because of side effects that make cataract surgery difficult. The frequent dosing (four times daily in glaucoma management) is also undesirable for some patients and may introduce adherence issues. Long-term use of pilocarpine has been known to cause irritation and follicular conjunctivitis; however, these issues are irrelevant for our pseudophakic patients.
CLINICAL EXPERIENCE
I have been treating four patient subtypes with pilocarpine 2% to alleviate the symptoms of displaced implants. In one case from January 2006, I treated an 86-year-old woman who had uneventful straightforward phacoemulsification in her right eye, with an injectable IOL. The implant was a single-piece hydrophilic acrylic IOL with an optic diameter of 5.75 mm. Her corrected postoperative visual acuity was 6/6. Six months later, she was referred to me with blurring and glare in her right eye.
Upon examination, the visual acuity was 6/18 and 6/6 in her right and left eyes, respectively, while she was wearing glasses. Slit-lamp examination showed a displaced implant, but the optic's edge was still above the geometric pupil center (Figures 1 and 2). The capsular bag showed some fibrosis; however, no signs of dehiscence or breaks in the capsule were present. Options for management, including the administration of pilocarpine, were discussed with the patient, who opted for the pilocarpine. Approximately 20 minutes after instillation of pilocarpine, the corrected vision returned to 6/6 (Figure 3). The patient was satisfied with these results. One year later, her visual acuity was still 6/6, and she was asymptomatic on just one drop of pilocarpine 2% once every morning.
IOL displacement is a recognized complication in some phaco procedures, and treatment in most moderate-to-severe cases is to reposition or replace the lens. Based on my clinical experience, I recommend that a conservative approach with pilocarpine should be presented as an alternative treatment for carefully selected patients. Remember to provide a full description of the potential risks and benefits.
A. Ibraheim DO, FRCS, FEBO, FRCOphth, is a Consultant Ophthalmologist (Barnsley) and Honorary Senior Clinical Lecturer, at Sheffield University, Barnsley District Hospital, South Yorkshire, UK. Dr. Ibraheim would like to acknowledge Hajir Ibraheim, who helped to compile the report. He may be reached at + 07810311639; asaibraheim@yahoo.co.uk.
