Red/Blue and Red/Green Glasses in Vision Therapy: MFBF, Anti-Suppression and the Evidence

Updated 2026-10-21

Written by the Optics Trainer team from published research, with every source linked below.

Red/blue and red/green glasses are among the cheapest ways to show each eye a different image, which is why they turn up in vision therapy activities, clinical tests and research on amblyopia treatment. This guide explains how anaglyph filters work, how they are used for monocular fixation in a binocular field (MFBF) and anti-suppression, the practical problems of ghosting and unequal brightness, and what the trials that used anaglyph glasses actually found.

How anaglyph glasses separate the two eyes

Anaglyph glasses put a different colour filter over each eye. Screen content drawn in one colour is visible through one filter and cancelled by the other, so each eye sees a different part of the display. This is one of several ways of presenting different images to the two eyes (dichoptic presentation), alongside polarised filters, mirror haploscopes, lenticular overlays, shutter glasses and head-mounted displays.

Red/blue and red/green pairs cannot carry a full-colour image and may look darker than red/cyan, Woods and Rourke note in their analysis of anaglyph ghosting. For therapy activities that is rarely a problem, because the goal is separation, not a realistic 3D picture.

Ghosting, filter quality and brightness

Separation is never perfect. Ghosting (crosstalk) happens when a filter lets through light outside its intended band, or when the display's colour primaries overlap, and the amount depends on the particular combination of glasses and screen. Software has to choose screen colours that the opposite filter cancels. The Worth 4 Dot app described by Webber and colleagues, for example, tuned each dot's colour so that it disappears through the other filter.

Filters also cut brightness, and not equally. In Webber's measurements, a flashlight Worth 4 Dot's white dot measured 620 cd/m² unfiltered, but only 12 cd/m² through the red filter and 55 cd/m² through the green. Filter quality varies too: in 25 trial boxes tested with camera images, the green filter leaked red light in 22 of them, and the authors recommended routine checks.

Check the patient's glasses against the display they will use. Ghosting depends on both.
Keep screen brightness consistent. One PEDIG trial and the Webber Worth 4 Dot app fixed brightness at maximum with auto-brightness turned off.
Wear the anaglyph glasses over the patient's spectacles, as the major trials did.
Check which filter goes over which eye for each activity. PEDIG placed the green filter over the amblyopic eye.

What MFBF is

Monocular fixation in a binocular field (MFBF) is a vision therapy approach that aims to stimulate the amblyopic eye's central vision while both eyes keep fusing the peripheral field. In a 2025 point-counterpoint opinion article in Clinical Insights in Eyecare, the authors arguing for the binocular approach describe MFBF as its starting point, first done with low-cost polarised or anaglyph materials and later extended by dichoptic video games; they cite no outcome evidence for MFBF itself. Bhombal and colleagues cite Cohen's 1981 paper, Monocular fixation in a binocular field, as the origin of the term.

The evidence for MFBF

We found no randomised trial that isolates MFBF. The published outcome data are small:

Jayakumar and colleagues (2020) compared MFBF software with patching in 54 children with anisometropic amblyopia over 6 months. Gains were similar (0.54 vs 0.37 logMAR), and the authors concluded MFBF was not superior to patching.
Bhombal and colleagues (2020) described 18 adults treated with red/blue anaglyph goggles at a touchscreen, combined with fusional exercises and 2 hours of patching. There was no control group, so the effect cannot be attributed to MFBF.
Suwal and colleagues (2024) studied an active vision therapy programme that included MFBF and red-green anaglyph anti-suppression tools in 65 children. Acuity gains were similar to patching, with larger stereoacuity gains, but the programme had several components.

Trials that used anaglyph glasses for amblyopia

The main dichoptic game trials, large and small, delivered treatment through red/green anaglyph glasses on an iPad or iPod, and their results are mixed:

PEDIG, 385 children aged 5 to 12: a falling-blocks game for 1 hour a day improved acuity 1.05 lines versus 1.35 with 2 hours a day of patching at 16 weeks, and did not meet noninferiority. Only 22% did more than 75% of the prescribed play.
PEDIG, 100 teenagers aged 13 to 16: 3.5 letters with the game versus 6.5 with patching, and only 13% did more than 75% of prescribed play.
PEDIG Dig Rush, 138 previously treated children aged 7 to 12: no benefit over glasses alone.
PEDIG Dig Rush, 182 children aged 4 to 6: a 0.5-line advantage over glasses alone at 4 weeks, inconclusive at 8 weeks.
BRAVO, 115 participants aged 7 and older: no better than a placebo game. The authors list compliance with the glasses as a possible reason.
Kelly and colleagues, 28 children: the game beat patching at 2 weeks, but not after crossover at 4 weeks.

Red/blue versus red/green in the evidence

The trials above all used red/green glasses. CureSight (510(k) K221375), the only anaglyph-based device we found among FDA amblyopia clearances (product code QQU), uses red/blue glasses together with eye tracking. In its randomised trial in 103 children aged 4 to under 9, it was noninferior to 2 hours a day of patching at 16 weeks. That result belongs to CureSight's device and protocol, not to anaglyph glasses in general.

The 2022 Cochrane review of binocular treatment found only one eligible trial, the PEDIG iPad study, with similar 16-week gains to patching in the subset of children aged 3 to 8, and concluded that long-term evidence is lacking.

Red/green filters in clinical tests

The same filters are used in diagnostic tests, where their limits also show. The Worth 4 Dot test uses red/green glasses for binocular dissociation, and in one retrospective chart review all 24 patients with congenital red-green colour vision defects but no strabismus or amblyopia still reported four dots. The TNO stereotest gives thresholds about twice those of other stereotests in children, and researchers suggest the red/green anaglyph separation may contribute.

Where Optics Trainer fits

Optics Trainer home activities run on a Quest headset, phone or tablet, with red/blue glasses for the activities that use them, and clinics set each patient's home program from the Optics Trainer dashboard. None of the trials above tested Optics Trainer, and their results do not apply to it. It is not a treatment for amblyopia or suppression and does not replace prescribed care.

Frequently asked questions

Why do children wear red and blue glasses in vision therapy?

The coloured filters let a screen or printed activity show each eye a different image. Clinicians use this to make the weaker eye work while both eyes stay open, for example in MFBF and anti-suppression activities.

What is MFBF in vision therapy?

Monocular fixation in a binocular field: an approach that aims to stimulate the amblyopic eye's central vision while both eyes keep fusing the peripheral field. It is often done with anaglyph or polarised materials. We found no randomised trial that tests MFBF on its own.

Is red/blue or red/green better for vision therapy?

We found no head-to-head trial. The large PEDIG and BRAVO trials used red/green glasses, and the FDA-cleared CureSight device uses red/blue. What matters in practice is that the glasses match the display and each filter fully cancels the colour meant for the other eye.

Do anaglyph binocular games work for amblyopia?

Results are mixed. A large PEDIG trial found a red/green iPad game did not match 2 hours of daily patching, trials in older children and adults found no benefit over glasses or placebo, and short-term gains in younger children were not clearly sustained.