Interventions for intermittent exotropia

Methodological quality of the review: High confidence

Author: Hatt SR, Gnanaraj L

Region: Not specified

Sector: Intermittent exotropia

Sub-sector: surgical treatments, non-surgical treatments

Equity focus: None Specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

Strabismus is known to be a condition in which the eyes are not normally aligned, in that one eye looks straight ahead while the other eye turns inwards, outwards, up or down. In childhood, most cases of strabismus could be present constantly, but some types are intermittent (only present sometimes). In intermittent exotropia (X(T)) an eye intermittently turns outwards (exotropia), typically more when looking into the distance, when tired or day-dreaming. When the child focuses on something close, the eye usually moves back to the centre. The clinical management of intermittent exotropia has been discussed extensively in the literature, yet there remains a lack of clarity regarding indications for intervention, the most effective form of treatment and whether or not there is an optimal time in the evolution of the disease at which any treatment should be carried out.

Research objectives

To determine the effectiveness of surgical and non-surgical treatment of X(T) in restoring ocular alignment and achieving or maintaining binocular single vision (BSV). The effect of factors such as age and subtype of X(T) were to be reported and if possible included in subgroup analyses.

Main findings

The authors found one randomized trial that met the inclusion criteria and therefore included it in the review. This included 36 patients with basic X(T) who were randomized to the different surgical procedures: bilateral rectus recession or unilateral lateral rectus recession with medical rectus resection. This trial showed that unilateral surgery was more effective than bilateral surgery for correcting the basic type of X(T).

This study was considered to have low risk of bias in terms of random sequence generation, allocation concealment, incomplete outcome data, selective reporting and other bias; and high risk of performance bias and detection bias.

The authors concluded that ‘The available literature consists mainly of retrospective case reviews, which are difficult to reliably interpret and analyse. The one randomized trial included found unilateral surgery more effective than bilateral surgery for basic intermittent exotropia. However, across all identified studies, measures of severity and thus criteria for intervention are poorly validated, and there appear to be no reliable natural history data. There is therefore a pressing need for improved measures of severity, a better understanding of the natural history and carefully planned clinical trials of treatment to improve the evidence base for the management of this condition.’

Methodology

The authors’ inclusion criteria consisted of randomized controlled trials that compared management strategies in people with X(T). Participants in the trials were people diagnosed with X(T), must have had evidence of exodeviation on cover test or prism cover test or other recognized methods for measuring ocular alignment. Interventions considered included surgical (any type of unilateral/bilateral surgery) and non- surgical (fusion or convergence exercises, occlusion, optical and botulinum toxin A injection). Primary outcome consisted of motor alignment at near- and distance-fixation and stereo acuity at near- using any age-appropriate test; and secondary outcomes included stereo acuity at distance-fixation and motor fusion test at near- or distance-fixation, or both.

A search was conducted on several electronic databases including Central, Medline, LILACS and Embase. No date or language restrictions were applied to searches. In addition, the British Orthoptic Journal from 1970 to 2002 and proceedings were searched for reports of trials; and reference lists of relevant studies for information on further relevant studies. Prior to the initial publication of this review in 2003, reviewers contacted researchers active in the field for information about further published or unpublished studies.

Two reviewers independently screened titles and abstracts to establish whether they the inclusion criteria and extracted data of included studies. Study quality was assessed according to the methods set out in Chapter 8 of the Cochrane Handbook for Systematic Reviews for Interventions.

Applicability/external validity

The basic type of X(T) constitutes a reasonably well defined subgroup of X(T), but it remains unclear how findings from the included trial may or may not apply to other subgroups of X(T). The included trial contributes improved evidence for the management of X(T), but there remain several major questions and areas in need of further research.

Geographic focus

The authors did not report the geographical location if the study included.

Quality assessment

Overall there is high confidence in the conclusions about the effects of interventions evaluated in this review. The authors conducted a thorough search of the literature to ensure that all published and unpublished trials were included in the review, avoiding language bias. Appropriate methods were used in terms of study selection, data extraction and quality and risk of bias assessment of included studies. The authors conducted a narrative synthesis of the results as only one study was identified for inclusion. In addition, due to the lack of reliable studies, they did not draw strong conclusions regarding optimal treatment.