A Systematic Review of Malyugin Rings in Cataract Surgery: Surgical Outcomes, Efficacy and Safety

2.1. Study Design

This systematic review was registered with PROSPERO (registration number: CRD420251069562) and abides by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist [13]. A PICOT framework was developed for the review (Supplementary Table 1), with a focus on an adult patient population undergoing cataract surgery with Malyugin rings as a dilating agent.

2.2. Search Strategy

A systematic literature search was conducted in 4 electronic databases: EMBASE (Ovid), MEDLINE (Ovid), CINAHL Plus (EBSCO), and Web of Science, from inception to October 21, 2024. Complete, verbatim search strategies for all 4 databases are provided in Supplementary Tables 2a–2d. All records were uploaded to Covidence^® for screening. No restrictions on year of publication, study design, or language were applied at the search stage; publication year and language were applied only as eligibility criteria at full-text screening. In addition to the 4 databases, the reference lists of all included studies and relevant reviews were hand-searched for further eligible records (none were identified). The search was updated on June 28, 2025, and no additional eligible studies were identified.

2.3. Study Selection

Studies were eligible if they were written in English, published after 2000, and involved adult patients undergoing cataract surgery in which the Malyugin ring was used as a pupil-expansion device. Eligible designs were randomized controlled trials (RCTs) and observational studies. To be included, studies had to report at least one relevant outcome, such as pupil dilation (measured by pupil diameter), duration of mydriasis, adverse effects (e.g., cardiovascular side effects, increased intraocular pressure), or intraoperative and postoperative complications.

Studies were excluded if they involved pediatric patients or individuals with contraindications to Malyugin rings or other mydriatic agents. Case reports, commentaries, reviews, and studies without comparison groups were also excluded, as were studies that failed to report relevant outcomes or provided insufficient data for extraction.

Titles and abstracts were screened independently and in duplicate by two reviewers (SA, FB) using Covidence. Full texts were then assessed independently and in duplicate by the same two reviewers, with reasons for exclusion recorded (language, population, study design, intervention, outcome, and date). Disagreements at any stage were resolved by discussion or, where consensus could not be reached, by adjudication from a third reviewer (JW). A PRISMA flow diagram summarizes the study selection process (Fig. 1).

2.4. Data Extraction and Synthesis

Data extraction was performed independently by two reviewers (SA, FB). Extracted information included authorship, publication year, country of study, study design, and sample size to provide context for each study. Patient details such as age, gender distribution, and comorbidities were also collected, along with intervention specifics, including dosage, comparator groups, and intervention duration, to facilitate interpretation and applicability of the findings to a broader population.

Data synthesis was conducted narratively, following the Synthesis Without Meta-analysis (SWiM) guideline. Study-level risk-of-bias judgements and the certainty of evidence for each reported outcome, rated using GRADE, are summarized in Supplementary Tables 3a and 3b, respectively. A quantitative meta-analysis was planned a priori but was not performed because no outcome was quantitatively poolable: for each candidate outcome, at most one study reported data in a compatible format (mean and standard deviation, or a 2×2 comparison against a common comparator), while the remaining studies reported medians and interquartile ranges, used non-equivalent comparators, or applied differing devices, sizes, outcome definitions, and follow-up windows (Supplementary Table 4). Because synthesis was narrative rather than quantitative, no formal power calculation or minimum information size was applicable. The accumulated sample of 3,233 eyes across 10 studies was nonetheless considered sufficient to support a narrative synthesis, in that it spans the clinically relevant contexts in which the device is used (small pupils, pseudoexfoliation syndrome, intraoperative floppy-iris syndrome, and femtosecond laser-assisted surgery), both commercially available ring sizes (6.25 mm and 7.0 mm), and all principal comparators (iris hooks, B-HEX and OASIS expanders, manual stretching, iris radial cuts, ophthalmic viscosurgical devices, and intracameral mydriatics), with consistent directions of effect within each outcome domain. The accumulated sample, however, was insufficient to permit quantitative pooling or to detect uncommon adverse events, and this is reflected in the GRADE ratings and limitations. All p-values reported in this review are those published by the primary studies; no additional statistical testing was undertaken by the review team. Each included study applied the conventional two-sided threshold of p < 0.05 to denote statistical significance, and significance is reported here as designated in the source publications. Any discrepancies in data extraction were resolved through discussion and consensus between the reviewers.

2.5. Risk of Bias Assessment

The risk of bias for studies included after full-text screening was assessed independently by two reviewers (SA, EA). For randomized controlled trials (RCTs), the Cochrane Risk of Bias Tool (RoB 2) was used to assess potential biases across selection, performance, detection, attrition, and reporting [14]. For observational studies, the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) tool was used to assess bias due to confounding, participant selection, intervention classification, deviations from intended interventions, missing data, outcome measurement, and selective reporting [15]. Any disagreements in bias assessments were resolved through discussion and consensus, or by consulting a third reviewer (FB).

3.1. Literature Search

A total of 449 publications were identified through comprehensive searches of 4 databases (EMBASE, n = 214; MEDLINE, n = 87; Web of Science, n = 137; CINAHL Plus, n = 11). After removing 151 duplicates, 298 records were screened, of which 271 were excluded. Altogether 27 reports were sought and assessed for eligibility, of which 17 were excluded at the full-text stage: 13 evaluated an intervention other than the Malyugin ring or did not provide extractable Malyugin ring–specific outcomes, 3 were not available in English, and 1 involved an ineligible patient population. A total of 10 studies met the inclusion criteria (Fig. 1).

3.2. Study Characteristics

In all, 10 studies (3,233 eyes) evaluated surgical outcomes with the Malyugin ring (Table 1) [3, 5, 8-12, 16-18]. Sample sizes ranged from 21 to 1,426 eyes, with mean ages 57.6–80 years, consistent with typical cataract populations. Most cohorts included both sexes, except Chang (2008), which enrolled only males [8]. Studies were conducted in Europe (n = 5), North America (n = 3), and Asia (n = 2), and were published between 2008 and 2024. Designs comprised 2 randomized trials, 4 prospective non-randomized studies, and 4 retrospective studies, with earlier reports (Chang 2008; Wilczynski et al. 2013) providing baseline comparisons. The evidence base thus comprised 2 randomized controlled trials (Gupta et al. 2024; Wilczynski et al. 2013) and 8 non-randomized studies, 2 of which (Fay et al. 2014; Hanna et al. 2014) are conference abstracts with limited methodological reporting [8, 9, 12, 17, 18]. This design mix, and the correspondingly mixed risk of bias (low to serious), should be borne in mind when interpreting all comparative findings below.

3.3. Safety and Postoperative Outcomes

Safety outcomes for the Malyugin ring were reported across 6 studies (Table 2). In a retrospective case series from the United Kingdom, Nderitu et al. found that the 7.0 mm Malyugin ring was associated with a higher incidence of postoperative inflammation and corneal edema compared to iris hooks [10]. Conversely, Borkenstein et al. conducted a prospective study in Austria involving patients with pseudoexfoliation syndrome and found that the 6.25 mm Malyugin ring was well tolerated, with minimal adverse events [16].

In the United States, Fay et al. retrospectively assessed changes in endothelial cell density (ECD) and concluded that Malyugin rings caused only minor ECD loss within safe clinical thresholds [17]. Wilczynski et al. similarly found less endothelial cell loss with Malyugin rings than with iris hooks, although more frequent pupil ovalization was observed with the device [9]. In contrast, Balal et al. reported that while Malyugin rings improved postoperative visual acuity, they also demonstrated a higher rate of iris tears relative to iris hooks and intracameral pupil expanders [3]. Hanna et al. found that the use of a Malyugin ring was associated with a slightly increased incidence of pseudophakic macular edema (PME) [18].

3.4. Efficacy of Pupil Dilation and Maintenance

All 8 studies reporting on the efficacy of pupil dilation supported the Malyugin ring’s ability to provide stable, sufficient mydriasis during cataract surgery (Table 3). Nderitu et al. found that the 7.0 mm Malyugin ring minimized the number of corneal incisions required during phacoemulsification [10]. Furthermore, in a prospective case series, Chang reported consistent 6.0 mm pupil dilation and reduced intraoperative complications when using a Malyugin pupil expansive device fashioned from 5-0 polypropylene [8].

In a large German clinical trial, Conrad-Hengerer et al. demonstrated successful dilation to >5.5 mm in the majority of SP cases using the 7.0 mm Malyugin ring [5]. Fay et al. corroborated these findings by noting consistent pupil dilation with only minor ECD loss [17]. Balal et al. affirmed the 6.25/7.0 mm Malyugin device’s effectiveness in SP cases, demonstrating efficient dilation across a large cohort [3].

Borkenstein et al. observed maintained pupil stability in cases of pseudoexfoliation syndrome, with a marked improvement in BCVA postoperatively (0.48 logMAR to −0.05 ± 0.13 logMAR) [16]. Similarly, Wilczynski et al. found that Malyugin ring-treated patients had significantly better postoperative BCVA than those treated with iris hooks (0.75 ± 0.30 vs. 0.56 ± 0.56; p < 0.05) [9]. Finally, Hanna et al. reported faster early visual recovery in the Malyugin group at both postoperative day 1 and week 1 (logMAR 0.20 vs. 0.58 at day 1; 0.23 vs. 0.48 at week 1, p < 0.05) [18].

3.5. Surgical Performance and Intraoperative Complications

A total of 4 studies assessed the intraoperative performance of the Malyugin ring (Table 4). In the United Kingdom, Nderitu et al. found that the use of the Malyugin ring during phacoemulsification was associated with shorter operative times than with iris hooks, with operative time also varying by surgeon grade (median 20 minutes for consultants vs. 32 minutes for trainees) [10]. Similarly, Wilczynski et al. reported a shorter mean phaco time in the Malyugin group compared to iris hooks (15.2 ± 3.9 s vs. 19.8 ± 3.1 s; p < 0.05) [9]. In Germany, Conrad-Hengerer et al. evaluated the use of the Malyugin ring in femtosecond laser-assisted cataract surgery. They found that the device enabled adequate pupil dilation in 68% of cases with small pupils, without any reported intraoperative complications [5].

Balal et al. observed that although intraoperative complication rates were generally comparable across Malyugin rings, iris hooks, and intracameral pupil expanders, the Malyugin group experienced a significantly greater rate of iris tears (p < 0.05) [3].

3.6. Comparative Outcomes to Other Pupil Expansion Devices

A total of 7 studies provided comparative analyses of the Malyugin ring and alternative pupil-dilation techniques (Table 5). Nderitu et al. reported shorter surgery duration with Malyugin rings; however, iris hooks demonstrated lower postoperative inflammation and edema [10]. Gupta et al. found that while both the Malyugin ring and B-HEX pupil expander maintained adequate visualization, the Malyugin ring was associated with significantly more pupillary distortion (p = 0.029) [12]. Conrad-Hengerer et al. demonstrated superior dilation success with the Malyugin ring relative to viscoadaptive mydriasis using ophthalmic viscosurgical devices (OVDs) or intracameral epinephrine [5].

Wang et al., in a six-arm prospective case-control study from China, found that the Malyugin ring achieved good BCVA (median 0.2 logMAR), moderate pupil diameter (median 4 mm), and well-preserved endothelial cell density (median postoperative ECD 1961 cells/mm²), whereas manual iris stretching was associated with the lowest postoperative density (1452 cells/mm²), indicating greater endothelial cell loss; the B-HEX and OASIS devices were less stable or harder to manipulate [11]. Balal et al. reported comparable visual acuity improvements across Malyugin ring, iris hooks, and intracameral phenylephrine, though iris tears were more frequent with the Malyugin ring (p < 0.05) [3]. Wilczynski et al. found better postoperative BCVA (0.75 vs. 0.56; p < 0.05) and lower endothelial cell loss (9.35% vs. 13.77%; p < 0.05) with the Malyugin ring than with manual iris stretching [9]. Lastly, Hanna et al. reported that the Malyugin group experienced significantly faster visual recovery than the iris hook group during the early postoperative period, although the pseudophakic macular edema rate was slightly higher [18].

3.7. Risk of Bias Findings

The overall risk of bias across the 10 included studies ranged from low to serious, with most demonstrating either low or moderate risk. Among the two studies evaluated using the RoB 2 tool (Fig. 2), Gupta et al. was judged to have an overall “low” risk of bias [12]. All domains (randomization process, deviations from intended intervention, missing outcome data, outcome measurement, and selective reporting) were rated as low risk, except for the final domain, which was flagged with “some concerns.” Wilczynski et al. was assigned an overall judgment of “some concerns” due to uncertainty in the randomization process and selective outcome reporting [9].

The remaining 8 studies were assessed using the ROBINS-I tool (Fig. 3). Wang et al., Balal et al., and Hanna et al. demonstrated consistently low risk of bias across all evaluated domains [3, 11, 18]. Nderitu et al., Conrad-Hengerer et al., and Borkenstein et al. were rated as having a “moderate” risk of bias due to limitations in confounding and participant selection [5, 10, 16]. Chang and Fay et al. were judged to be at “serious” risk of bias; for Chang this was largely due to serious concerns regarding confounding, whereas Fay et al. raised concerns about both confounding and participant selection [8, 17]. A study-level risk-of-bias summary is provided in Supplementary Table 3a. Applying GRADE, the certainty of evidence was low to very low for all reported outcomes, driven principally by risk of bias and imprecision (Supplementary Table 3b); this is reflected in the consolidated outcome summary (Supplementary Table 5) and is carried forward into the Discussion.

4.1. Strengths and Limitations

This systematic review provides a structured synthesis of the efficacy and safety of Malyugin rings as a pupil expansion device in cataract surgery. The review followed the PRISMA guidelines and employed a dual-reviewer process for study selection, data extraction, and risk of bias assessment, thereby reducing selection and reporting biases. Risk of bias was rigorously assessed using both the RoB 2 tool for randomized controlled trials and the ROBINS-I tool for observational studies, increasing the credibility and transparency of the findings. Additionally, including studies across a wide range of countries and surgical contexts enhances the external validity of the results. Many of the included studies were prospective in design, allowing for more consistent data collection and minimizing recall bias.

This review has several limitations. Considerable heterogeneity was observed across studies, particularly in terms of surgical technique, device size (6.25 mm vs. 7.0 mm), comparator interventions (e.g., iris hooks, B-HEX, OVDs), and outcome measures such as BCVA, endothelial cell loss, and surgical time. The inclusion of both randomized and non-randomized studies introduced methodological heterogeneity that may affect the strength of our conclusions. Finally, some studies lacked complete reporting of key variables such as gender distribution, follow-up duration, and surgeon experience, which may introduce residual confounding. In addition, 4 additional limitations warrant emphasis. First, no outcome could be quantitatively synthesized: reporting was heterogeneous (means with SD versus medians with interquartile ranges), comparators were non-equivalent, and outcome definitions and follow-up windows differed; therefore, only a narrative synthesis was possible, and certainty of evidence was low to very low across outcomes (GRADE). Second, follow-up was short and heterogeneous across studies (predominantly ≤1 month, with only a subset reporting to 3–6 months), precluding conclusions about long-term endothelial, refractive, or pupil-shape outcomes. Third, although no language restriction was applied at the search stage, English-language eligibility at the full-text stage resulted in the exclusion of 3 records. As only 3 records were excluded on language grounds, the likely impact on the conclusions is small; however, language bias cannot be completely excluded. Fourth, 2 included records are conference abstracts with limited methodological detail, further weakening the evidence [17, 18].