Risk and protective factors of late in-the-bag intraocular lens dislocations: systematic review

Author: Gabriel M, Mester A, Mayer-Xanthaki C. 

Geographical coverage: Not reported

Sector: Intraocular lens

Sub-sector: Risk and prevention

Equity focus:  Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Cataract surgery is one of the most frequently performed and cost-effective operations worldwide, substantially improving vision and quality of life. A key step is the implantation of an intra-ocular lens (IOL) into the capsular bag, where it is expected to remain centred and stable. In rare cases, however, the entire capsular bag–IOL complex dislocates months or years later, causing serious visual impairment. These late in-the-bag (ITB) dislocations are distinct from out-of-the-bag dislocations, in which only the IOL shifts position, and usually require more complex corrective surgery. As the global volume of cataract operations rises, understanding and preventing this sight-threatening complication has become increasingly important.

Objective: To provide a structured analysis of risk and protective factors for late ITB IOL dislocation, enabling clinicians to gauge individual patient risk and to plan appropriate management.

Main findings:

Evidence base: Thirty-nine eligible studies (predominantly retrospective; three prospective) comprising 18 614 cases of late ITB dislocation.

Incidence and timing: Dislocation typically occurred 6–11 years after surgery, with a cumulative 10-year incidence of 0.1 %–1 %. Affected patients were usually 70–85 years old, with a slight male predominance.

Risk factors (strong evidence) include pre-operative trauma, zonular dehiscence, previous vitrectomy, retinitis pigmentosa, pseudo-exfoliation (PEX), high myopia, glaucoma or previous glaucoma surgery, corneal endothelial damage, uveitis, IOL characteristics: hydrophilic material, quadripode design, or marked haptic angulation. Protective factors, include capsular tension rings (CTRs), Nd:YAG capsulotomy, three-piece IOLs, IOLs with large optic diameters.

Roughly one-quarter of dislocations occurred in eyes with no identifiable risk factor.

Methodology:

A single-database search of PubMed (February 2020) identified English- and German-language studies with ≥ 20 patients that examined risk factors for late ITB dislocation. Reference lists of included articles were hand-searched for further studies. Screening, data extraction and quality assessment (Cochrane RoB tools) were performed—but the number of reviewers was not reported. Owing to heterogeneity, findings were synthesised narratively.

Applicability/external validity:

Generalisability is limited by the predominance of retrospective studies, variation in surgical technique, IOL design and patient characteristics, and the absence of standardised reporting. While factors such as PEX and trauma were consistently important, the lack of prospective, multicentre data may restrict applicability to contemporary practice.

Geographic focus:

No geographical restrictions were imposed, but the distribution of included studies was not reported.

Summary of quality assessment:

Confidence in the conclusions is low. Although inclusion/exclusion criteria were explicit and study quality was assessed with recognised tools, the search strategy was restricted to one database and two languages, and no list of excluded studies was provided. Unreported reviewer processes further weaken reliability.