Interventions for convergence insufficiency: a network meta-analysis

Author: Scheiman M, Kulp MT, Cotter SA, Lawrenson JG, Wang L, Li T.

Geographical coverage: The US, Iran and Egypt

Sector: Biomedical

Sub-sector: Treatment

Equity focus: Study examines results for children aged under 18 years separately.

Study population: Children and adults with symptomatic convergence insufficiency.

Review type: Effectiveness review

Quantitative synthesis method: Network meta-analysis

Qualitative synthesis method: Not applicable

Background: Convergence insufficiency is a binocular vision disorder where the eyes tend to drift outward, making it difficult to focus inward during close work. Treatments include prism-lensed reading glasses for visual comfort and vision therapy to restore normal function. Vision therapy, aimed at improving the eyes’ ability to turn inward, can be self-administered at home using pencil push-ups or computer software, or it can be prescribed and monitored by a doctor, administered by trained therapists in an office setting with home practice.

Objectives: To assess the comparative effectiveness and relative ranking of non-surgical interventions for convergence insufficiency through a systematic review and network meta-analysis (NMA).

Main findings:

This review indicates that for children, office-based convergence/accommodative therapy supplemented with home reinforcement is more beneficial than either home-based pencil/target push-ups or home-based computer convergence/accommodative therapy. However, the efficacy of different non-surgical interventions for adults is not as well-defined.

The review discusses a study that included 12 trials with 1289 participants, focusing on seven interventions for convergence insufficiency. The interventions included various forms of office-based and home-based therapies, prism reading glasses, and placebo interventions. Six of these trials, conducted by the Convergence Insufficiency Treatment Trial (CITT) Investigator Group, involved 968 pediatric participants. The results showed that office-based vergence/accommodative therapy with home reinforcement was more effective than other methods in achieving treatment success, defined as both clinical measures of convergence being normal and showing a pre-specified magnitude of improvement. However, authors identified no significant difference in treatment success between home-based computer vergence/accommodative therapy and home-based pencil/target push-ups, or between either of the two home-based therapies and placebo therapy.

No adverse effects related to study treatments were reported for any of the included studies. Excellent adherence was reported for office-based convergence/accommodative therapy (96.6% or higher) in two trials. Reported adherence with home-based therapy was less consistent, with one study reporting decreasing adherence overtime (weeks 7 to 12) and lower completion rates with home-based pencil/target push-ups.

Clinical heterogeneity was found in several aspects, mainly in the age distribution of trial participants.

Risk of bias was evaluated in each of the 12 included trials, using eight pre-specified criteria. Three trials were judged to have high potential for bias in two domains. Ten trials were judged to have unclear risk of bias in two or more domains.

The document highlights several research gaps in non-surgical interventions for convergence insufficiency. These include the effectiveness of different office-based and home-based therapy procedures, the potential of telemedicine or virtual formats to enhance home-based therapies, and the possibility of increasing access and cost-effectiveness by replacing some office-based visits with virtual ones. It also questions if there’s a more effective method of prescribing prism based on fixation disparity testing. The impact of successful treatment on health-related quality of life and potential disparities in access to care due to insurance limitations are also areas of interest. More studies on adults are needed due to the low certainty of evidence for treatment effectiveness.

Methodology:

Inclusion criteria were as follows: randomised controlled trials (RCTs) examining any form of non-surgical intervention versus placebo, no treatment, sham treatment, or other non-surgical interventions. For this review, convergence insufficiency is defined as a condition characterised by a larger exophoria at near than at far, and one or both two objective clinical signs: a receded near point of convergence (6 cm or greater); insufficient PFV at near.

A Cochrane Eyes and Vision Information Specialist conducted a comprehensive search for randomised controlled trials and controlled clinical trials in several databases, with no language or publication year restrictions. The databases, last searched on 20 September 2019, included the Cochrane Central Register of Controlled Trials, Medline Ovid, EMBASE, PubMed, metaRegister of Controlled Trials, US National Institutes of Health Ongoing Trials Register, and the WHO International Clinical Trials Registry Platform. Additional trials were identified by searching reference lists of trial reports and using the Science Citation Index to find studies citing the included trials. Primary investigators were contacted for additional trial details when necessary. Manual searches were also conducted in specific journals from various years.

At least two authors independently reviewed the titles and abstracts resulting from searches according to the eligibility criteria. Included studies were assessed further for their methodological quality using the Cochrane risk of bias tool. At least two review authors independently extracted the data onto paper data collection forms. They resolved discrepancies through discussion. One review author entered all data into Review Manager. Data was verified by a second author.

For dichotomous outcomes, a summary risk ratio was computed, and for continuous outcomes, the mean difference between interventions was calculated by the auhtors. The effect estimate and its 95% confidence intervals were reported. In terms of unit of analysis, a person-based analysis was performed as convergence insufficiency is a binocular vision disorder. None of the reviewed trials used a cluster or cross-over design. All eligible treatment groups from multi-arm trials were included in the NMA without any group combinations.

Heterogeneity was assessed both clinically and methodologically by qualitatively examining the characteristics of each included trial. Statistical heterogeneity was quantitatively evaluated using the Chi 2 test and the I² values. It was pre-determined that a p value of less than 0.1 from the Chi 2 test and an I² statistic of greater than 50% would indicate significant statistical heterogeneity. It was planned to use a funnel plot to assess publication bias if a sufficient number of trials were identified.

Data synthesis consisted of two networks of trials. One comprised the trials with children as participants and the other the trials with adult participants. For each network, a pairwise meta-analysis was first conducted for every direct comparison using a random-effects model.

Applicability/external validity: Authors indicate imprecision of NMA estimates and heterogeneity in the relative effects of interventions limited the applicability of the evidence for the adult population (meaning that, for most comparisons, the level of certainty was low). However, in the children’s network, the overall certainty of evidence was high for all comparisons involving office-based convergence/accommodative therapy and moderate-certainty to low-certainty for comparisons between the two home-based interventions.

Authors note that findings from the review are consistent with findings from older narrative reviews on the same topic, none of which included a meta-analysis.

Geographic focus: Eight of the included trials were conducted in the US and the remaining four studies in upper‐middle‐income (Iran) or lower‐middle‐income (Egypt) countries. Authors do not consider how findings may vary on a country-by-country basis.

Summary of quality assessment:

The approaches to the identification, inclusion and appraisal of studies were highly robust, with all stages being undertaken to high standards by at least two authors, and the search being unrestricted in terms of language, date or publication status. While the approach to the analysis was also highly robust, due to the small numbers of studies involved, the authors were unable to determine how the inclusion of studies of lower quality influenced the reported results. For these reasons, we have medium confidence in the findings of this review.