How do different treatments for the vision disorder, convergence insufficiency, compare in effectiveness?

Why is this question important?
Convergence insufficiency is a common vision disorder in which a person's eyes tend to drift outwards when they try to use their eyes together up close. This can cause eye strain, headaches, blurred and double vision. When reading, people with convergence insufficiency frequently lose their place or have to re-read text.

There are two main types of treatment for convergence insufficiency: 1) prism-lensed reading glasses, designed to improve visual comfort, and 2) eye (vision) therapy designed to restore normal visual function and improve visual comfort.

Different types of vision therapy are prescribed for the treatment of convergence insufficiency that aim to improve the affected person’s convergence ability (the ability of eyes to turn inwards). Treatment can be self-administered at home using only a pencil (pencil push-ups) or a computer software program (home-based computer therapy). Alternatively, it can consist of a sequence of activities individually prescribed and monitored by the doctor, administered by trained therapists in an office setting along with practice at home (office-based therapy with home reinforcement).

We reviewed the evidence from research studies to compare the effectiveness of these different treatments (prism reading glasses, office-based therapy with home reinforcement, and home-based treatments), and also to determine whether the treatments are associated with adverse (unwanted) effects.

How did we identify and evaluate the evidence?
First, we searched the medical literature for randomized controlled studies (clinical studies where people are randomly put into one of two or more treatment groups). This type of study provides the strongest evidence about the effects of a treatment. We compared the results and summarized the evidence from all the studies. Finally, we assessed how certain the evidence was by considering factors such as the way studies were conducted, the number of people in the studies, and the consistency of findings across studies. Based on our assessments, we categorized the evidence as being of very low-, low-, moderate-, or high-certainty.

What did we find?
We found 12 studies with a total of 1289 people with convergence insufficiency. Six studies were conducted in children aged seven to 18 years, five studies in young adults aged 15 to 40 years, and one study in adults aged 40 years and older. Studies lasted for between six weeks and six months.

Results in children
For improving convergence ability, high-certainty evidence showed that office-based therapy with home reinforcement is better than placebo, home-based computer therapy, and home-based pencil push-ups.

For improving convergence ability, as well as symptoms reported by children (such as headaches or frequent loss of place when reading), low- to moderate-certainty evidence suggested that office-based therapy with home reinforcement is better than placebo, home-based computer therapy, and home-based pencil push-ups.

It is not clear (low- to moderate-certainty evidence) whether there is a difference for improving convergence alone, or convergence and symptoms as reported by children, between home-based computer therapy and home-based pencil push-ups, or between these two home-based treatments and placebo.

One study compared prism reading glasses against placebo reading glasses, and found no evidence of a difference in improvement in convergence or symptoms.

Results in adults
Evidence from three studies indicated that office-based therapy could be more effective than placebo for improving convergence when it was measured one way (‘positive fusional vergence’), but not when measured another way (‘near point convergence’). There was no difference between treatments for changes in symptoms reported by adults.

One study compared glasses with prism lenses against placebo glasses, and found that adults with prism glasses reported fewer symptoms. However, there was no evidence of a difference for improvement in convergence.

Are there any adverse effects from treatment?
No study, in children or adults, reported any adverse effects related to study treatments.

What does this mean?
High-certainty evidence indicates that, office-based therapy with home reinforcement is more effective than home-based pencil push-ups, home-based computer therapy, and placebo for treating convergence insufficiency in children. For adults, the comparative effects of these interventions are less clear.

How-up-to date is this review?
The evidence in this Cochrane Review is current to September 2019.

Authors' conclusions: 

Current research suggests that office-based vergence/accommodative therapy with home reinforcement is more effective than home-based pencil/target push-ups or home-based computer vergence/accommodative therapy for children. In adults, evidence of the effectiveness of various non-surgical interventions is less clear.

Read the full abstract...
Background: 

Convergence insufficiency is a common binocular vision disorder in which the eyes have a strong tendency to drift outward (exophoria) with difficulty turning the eyes inward when reading or doing close work.

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).

Search strategy: 

We searched CENTRAL, MEDLINE, Embase, PubMed and three trials registers up to 20 September 2019.

Selection criteria: 

We included randomized controlled trials (RCTs) examining any form of non-surgical intervention versus placebo, no treatment, sham treatment, or other non-surgical interventions. Participants were children and adults with symptomatic convergence insufficiency.

Data collection and analysis: 

We followed standard Cochrane methodology. We performed NMAs separately for children and adults.

Main results: 

We included 12 trials (six in children and six in adults) with a total of 1289 participants. Trials evaluated seven interventions: 1) office-based vergence/accommodative therapy with home reinforcement; 2) home-based pencil/target push-ups; 3) home-based computer vergence/accommodative therapy; 4) office-based vergence/accommodative therapy alone; 5) placebo vergence/accommodative therapy or other placebo intervention; 6) prism reading glasses; and 7) placebo reading glasses.

Six RCTs in the pediatric population randomized 968 participants. Of these, the Convergence Insufficiency Treatment Trial (CITT) Investigator Group completed four RCTs with 737 participants. All four CITT RCTs were rated at low risk of bias. Diagnostic criteria and outcome measures were identical or similar among these trials. The four CITT RCTs contributed data to the pediatric NMA, incorporating interventions 1, 2, 3 and 5. When treatment success was defined by a composite outcome requiring both clinical measures of convergence to be normal, and also show a pre-specified magnitude of improvement, we found high-certainty evidence that office-based vergence/accommodative therapy with home reinforcement increases the chance of a successful outcome, compared with home-based computer vergence/accommodative therapy (risk ratio (RR) 1.96, 95% confidence interval (CI) 1.32 to 2.94), home-based pencil/target push-ups (RR 2.86, 95% CI 1.82 to 4.35); and placebo (RR 3.04, 95% CI 2.32 to 3.98). However, there may be no evidence of any treatment difference between home-based computer vergence/accommodative therapy and home-based pencil/target push-ups (RR 1.44, 95% CI 0.93 to 2.24; low-certainty evidence), or between either of the two home-based therapies and placebo therapy, for the outcome of treatment success.

When treatment success was defined as the composite convergence and symptom success outcome, we found moderate-certainty evidence that participants who received office-based vergence/accommodative therapy with home reinforcement were 5.12 (95% CI 2.01 to 13.07) times more likely to achieve treatment success than those who received placebo therapy. We found low-certainty evidence that participants who received office-based vergence/accommodative therapy with home reinforcement might be 4.41 (95% CI 1.26 to 15.38) times more likely to achieve treatment success than those who received home-based pencil push-ups, and 4.65 (95% CI 1.23 to 17.54) times more likely than those who received home-based computer vergence/accommodative therapy. There was no evidence of any treatment difference between home-based pencil push-ups and home-based computer vergence/accommodative therapy, or between either of the two home-based therapies and placebo therapy.

One RCT evaluated the effectiveness of base-in prism reading glasses in children. When base-in prism reading glasses were compared with placebo reading glasses, investigators found no evidence of a difference in the three outcome measures of near point convergence (NPC), positive fusional vergence (PFV), or symptom scores measured by the Convergence Insufficiency Symptom Survey (CISS).

Six RCTs in the adult population randomized 321 participants. We rated only one RCT at low risk of bias. Because not all studies of adults included composite success data, we could not conduct NMAs for treatment success. We thus were limited to comparing the mean difference (MD) between interventions for improving NPC, PFV, and CISS scores individually using data from three RCTs (107 participants; interventions 1, 2, 4 and 5). Compared with placebo treatment, office-based vergence accommodative therapy was relatively more effective in improving PFV (MD 16.73, 95% CI 6.96 to 26.60), but there was no evidence of a difference for NPC or the CISS score. There was no evidence of difference for any other comparisons for any outcomes. One trial evaluated base-in prism glasses prescribed for near-work activities and found that the prism glasses group had fewer symptoms compared with the placebo glasses group at three months (MD -8.9, 95% CI -11.6 to -6.3). The trial found no evidence of a difference with this intervention in NPC or PFV.

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

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