In-the-bag intraocular lens dislocation: A ticking time bomb

“No problem can be solved from the same level of consciousness that created it.” —Albert Einstein The World Health Organization estimates that the number of cases of blindness from cataract will increase to 40 million in 2025 because of the aging population and longer life expectancies.A There is robust evidence to demonstrate that the cataract surgical rate has been on an upward trend.1 Cataract surgery techniques are being constantly refined with the introduction of technological advancements. The fundamental changes have been in transition from intracapsular cataract extraction (ICCE) in the 1960s and 1970s, to extracapsular cataract extraction (ECCE) in the 1980s and 1990s, to the current technique of sutureless small-incision phacoemulsification surgery with injectable intraocular lens (IOL) implantation. These surgical transitions have had good scientific credibility, showing measurable improvements in visual outcomes and safety. The randomized Madurai IOL study showed for the first time the superiority of ECCE with posterior chamber IOLs over ICCE in terms of visual acuity restoration and safety.2 Similarly, a randomized clinical trial comparing ECCE with phacoemulsification found phacoemulsification to be clinically superior and cost-effective.3 Currently, sutureless clear corneal incision, continuous curvilinear capsulorhexis (CCC), phacoemulsification, and in-the-bag placement of a foldable IOL represent the gold standard for routine cataract surgery. Technological advances and standardized surgical techniques have resulted in cataract surgery being extremely successful with a low complications rate. Several international population studies have examined aggregate incidence and risk factors for surgery-related complications, including national efforts in the United Kingdom,4 Australia,5 Sweden,6 and Malaysia,B among others. The major intraoperative complication during cataract surgery is posterior capsule rupture with a reported incidence between 2% to 3%.B,C One of the most sight-threating postoperative complications is the development of cystoid macular edema (CME). In the recently reported National Ophthalmology Database Audit in the UK the incidence of CME was 1.3%.C Modern endocapuslar phacoemulsification combined with CCC and foldable/injectable IOLs have provided a safe and stable environment for the long-term stability of the IOL within the intact capsular bag. However, radial tears in the anterior capsule or poor surgical technique may result in IOL dislocation in the early postoperative period. Late spontaneous IOL dislocation is defined as IOL dislocation within the capsular bag occurring 3 months following uncomplicated cataract surgery.7 This complication of late IOL dislocation stems from zonular weakness. One of the earliest reports of late spontaneous IOL dislocation was by Boke et al. in 1985.7 In a histopathological study of post-mortem eyes with pseudoexfoliation (PEX), Auffarth et al. demonstrated pronounced decentration of IOLs compared with normal eyes.8 This finding is attributed to decentration of the entire capsular bag because of zonular weakness and damage. Davidson in 19939 and later Nishi et al. in 199610 reported two cases of spontaneous IOL dislocation secondary to capsular contraction syndrome and attributed the IOL dislocation to excessive centripetal force on the zonular apparatus. The first report on spontaneous late IOL dislocation within the capsular bag in patients with PXE was in 2001 by Jehan et al.11 Eight eyes of 7 patients with PXE developed spontaneous IOL dislocation at a mean of 85 months following uncomplicated cataract surgery. All of them required surgical intervention and pathological examination revealed intact capsular bag in all cases. In 2009, Davis et al.12 reported the largest series to date on late in-the-bag IOL dislocation. They analyzed 86 eyes of explanted late in-the-bag IOL dislocation. In this series the mean time interval between cataract surgery to spontaneous IOL dislocation was 8.5 years. The predisposing factors were PXE, prior vitreoretinal surgery, history of trauma, and uveitis.12 The other predisposing factors that have been reported to cause late IOL–bag dislocation include trauma, high myopia, vitreoretinal surgery, retinitis pigmentosa, and connective tissue disorders, such as Marfan syndrome, homocystinuria, hyperlysinemia, Ehler-Danlos syndromes, scleroderma, and Weil-Marchesani syndrome. The incidence of late in-the-bag IOL dislocation may be underreported. Gimbel et al.,13 in a review published in this journal in 2005, reported on 72 such cases up to 2004. However, an increase in the rate of in-the-bag IOL dislocations has been reported in the past decade.14–17 Lorente et al.18 proposed a grading system for complex late in-the-bag IOL dislocation as follows: grade 1: pseudophakodonesis; grade 2: dislocation of the capsular bag with the superior edge of the IOL above the visual axis; grade 3: the superior edge of IOL remains below the visual axis, with a severe decrease in visual acuity; grade 4: IOL dislocated into the vitreous cavity. In this issue (page 305) Bulnes et al. report the largest series to date on late in-the-bag IOL dislocation. In this study of 134 eyes, the authors found a significant trend toward a decrease in intraocular pressure as the grade of IOL dislocation increases. I feel that spontaneous late in-the-bag IOL dislocation may be more common than we think. Even though there are more published reports on this in the last decade what we are seeing may be just the tip of the iceberg. There is an increasing trend for early intervention for lens-based surgery, either for refractive correction or for cataract. With the increased life expectancy combined with increasing psuedophakia in the population, the incidence of late in-the-bag IOL dislocation may well be on the upward trend. As surgeons we need to be mindful of preoperative risk factors and modify our surgical techniques to mitigate this potentially dangerous complication. This may well include adequate CCC, meticulous capsular polishing, use of capsular tension rings in high-risk cases and even consideration of placing a 3-piece IOL in the sulcus with anterior optic capture. Also, newer initiatives to collect internationally standardized data on cataract surgery outcomes (ie, International Consortium for Health Outcomes Measurement, American Academy of Ophthalmology IRIS Registry [Intelligent Research in Sight], and the European Registry of Quality Outcomes for Cataract and Refractive Surgery) will help to provide better understanding of this complication.