Summary of Findings

PICO (1.1)

Population: Children with Down syndrome

Intervention: Bifocal glasses

Comparator: Usual care

1. Primary study [3] Baseline/comparator Control arm of reference used for intervention [3]
2. Risk of Bias: serious. Inadequate/lack of blinding of participants and personnel, resulting in potential for performance bias, Inadequate/lack of blinding of outcome assessors, resulting in potential for detection bias; Imprecision: serious. Wide confidence intervals, only data from one study;
3. Near visual acuity
4. Primary study Supporting references [1].
5. Risk of Bias: serious. Inadequate/lack of blinding of participants and personnel, resulting in potential for performance bias, Carryover effects in crossover trial; Imprecision: serious. Only data from one study;
6. Systematic review Supporting references [2].
7. Risk of Bias: serious. Inadequate/lack of blinding of participants and personnel, resulting in potential for performance bias, Inadequate/lack of blinding of outcome assessors, resulting in potential for detection bias, Treatment and control group not comparable on baseline characteristics of outcome measures.; Imprecision: serious. Only data from one study;

Description of studies

A total of three studies were included in the analysis of the literature. Important study characteristics and results are summarized in table 2.

Table 2. Characteristics of included studies

*For further details, see risk of bias table under the tab ‘Evidence tabellen’

Results

Near visual acuity

One study (De Weger, 2019) reported on near visual acuity. They compared bifocal glasses with unifocal glasses in 119 children with Down syndrome aged two to sixteen years in a RCT. Sixty-six percent of the study population wore unifocal glasses (usual care) at the beginning of the study. Near visual acuity improved at one year after the start of wearing bifocal glasses, compared to the control (unifocal glasses) (p<0.001). The difference in near visual acuity between bifocal glasses and unifocal glasses at six weeks and six months of follow-up was not statistically significant. Near visual acuity improved during the year and the difference between the intervention groups was statistically significant at one year.

Distant visual acuity

One study (De Weger, 2019) reported on distant visual acuity. They compared bifocal glasses with unifocal glasses in 119 children with Down syndrome aged two to sixteen years. Sixty-six percent of the study population wore unifocal glasses (usual care) at the beginning of the study. Distant visual acuity improved in both groups and was not significantly different at six weeks, six months, and one year after the start of wearing bifocal glasses, compared to the control (unifocal glasses) (p=0.577).

Ocular alignment/strabismus

One study (De Weger, 2020) reported on ocular alignment/strabismus. They compared bifocal glasses with unifocal glasses in 119 children with Down syndrome aged two to sixteen years. Sixty-six percent of the study population wore unifocal glasses (usual care) at the beginning of the study. Ocular alignment improved at six weeks, six months, and one year after the start of wearing bifocal glasses, compared to the control (unifocal glasses) (p<0.001), resulting in straight eyes or micro to small strabismus in de bifocal group.

Executive function

One study (De Weger, 2021) reported on executive function (measured by the Minnesota executive function scale, MEFS; BRIEF-P and BRIEF). They compared bifocal glasses with unifocal glasses in 119 children with Down syndrome aged two to sixteen years. Sixty-six percent of the study population wore unifocal glasses (usual care) at the beginning of the study. Executive function improved at one year after the start of wearing bifocal glasses, compared to the control (unifocal glasses) (p<0.001).

Search and select

A systematic review of the literature was performed to answer the following question(s):

a. What is the place of treatment with bifocal spectacles in children with Down syndrome and an eye defect?

b. What is the place of treatment for keratoconus?

Table 1. PICO

Relevant outcome measures

The guideline panel considered visual functions and executive functions as a critical outcome measure for decision making; and quality of life as an important outcome measure for decision making.

The guideline panel defined an increase or decrease of 25% as a minimal clinically (patient) important difference.

Search and select (Methods)

The databases Medline (via OVID) and Embase (via Embase.com) were searched with relevant search terms until April 24, 2024. The detailed search strategy is listed under the tab ‘Literature search strategy’. The systematic literature search resulted in 279 hits. Studies were selected based on the following criteria: relevance to PICO, study in English or in Dutch, systematic review, randomized controlled trial or observational cohort study. Three studies were initially selected based on title and abstract screening. After reading the full text, no studies were excluded, and three studies were included for intervention A (bifocal glasses). No studies were included for intervention B (cross-linking for children with keratoconus).