Table 1.

Methodological characteristics of studies included in the review.

Study	Sample type and size	Intervention	Characteristics of the PL group	Outcome measure
Hess et al., 201412	•N = 14 •Age range: 13–50 years •Type of amblyopia: A(n = 7), S(n = 5), C(n = 2)	•VG (Tetris) in a dichoptic format with lenticular screen (n = 5) or anaglyph (n = 9) presentation in IpodTouch at home •Duration of exposure (both): 10 h to 30 h •Home (both)	•Antisuppression DT (lenticular screen / anaglyphic version) •PVG (Tetris)	•VA •Stereo acuity
Mansouri et al., 201413	•N = 22 •Age range: 5–73 •Mean age: 36.2 ± 20.3 years •Type of amblyopia: A(n = 7), S(n = 15)	•Random dot kinematograms were presented dichoptically to identify the direction of motion of the targets •Duration of exposure: 2 h/session, 1000 trials/session, 18 sessions, 6 weeks (total: 36 h) •Laboratory / Clinic	•Antisuppression DT (video stereo-google) •Motion identification task (initial contrast of the target and noise dots is 100% and 0% respectively)	•VA
Xi et al., 201414	•N = 11 •Mean age: 21.1 ± 5.1 years •Age range: 11–27 years •Type of amblyopia: A(n = 8), I(n = 3)	•Different texture anaglyphs with different disparities with red/green glasses •Duration of exposure: 10–13 sessions •Laboratory / Clinic	•Stereopsis (anaglyph textures)	•Disparity threshold •Stereo acuity •VA
Zhang et al., 201415	•N = 19 •Mean age: 22.5 years •Age range: 19–27 years •Type of amblyopia: A(n = 12), S(n = 2), C(n = 5)	•Gabor stimulus. Configurations for contrast, orientation and Vernier discrimination at one orientation •2 stages: low and high spatial frequency •Duration of exposure: 2 h/session, 30 sessions (total: 60 h) •Laboratory / Clinic	•MT •Grating contrast detection (Gabor patch)	•VA •Stereo acuity •CS (untrained orthogonal orientation)
Birch et al., 201516	•N = 50 •Mean age: 5.6 ± 0.9 years •Type of amblyopia: A(n = 16), S(n = 11), C(n = 23)	•Binocular iPad games + patching (n = 45) •Sham iPad games + patching (control) (n = 5) •Duration of exposure (both): iPad: 4 h/week, 4 weeks (total: 16 h); patching: 2 h/day at a different time of game •Laboratory / Clinic (both)	•Antisuppression DT (anaglyphic version) •PVG (Game pieces: blocks, balloons, balls, paddles)	•VA •Stereo acuity
Khan et al., 201517	•N = 61 •Age range:12–30 years •Mean age:17 years •Type of amblyopia: A(n = 61)	•Occlusion therapy of better eye with on near visual task (VG, computers, mobile phone gaming, colouring patterns) •Duration of exposure: 2−4 h/day, end-point of therapy was considered as stable VA maintained at least three months of occlusion •Home	•MT •Near visual task (VG an others)	•VA
Li SL et al., 201518	•N = 8 •Mean age = 7.4 ± 2.0 years •Age range = 4–10 years •Type of amblyopia: A(n = 3), S(n = 1), C(n = 4)	•Watching 3 dicoptic movies per week, 2 weeks on a passive 3D screen •Duration of exposure: 9.4 ± 0.9 h •Laboratory / Clinic	•Antisuppression DT (polarized version) •Movie viewing	•V •Stereo acuity •Interocular suppression
Li J et al., 201519	•N = 30 •Mean age = 22.2 ± 3.5 years •Age range = 17–31 years •Type of amblyopia: A(n = 20), S(n = 9), C(n = 1)	•Dichoptic VG presented on iPod touch equipped with a lenticular overlay screen combined with tDCS (n = 15) •Dichoptic VG viewed through video goggles combined with MT (n = 15) •Duration of exposure (both): 5 days/week, 2 weeks •Laboratory / Clinic (both)	•MT + Antisuppression DT (video googles) •tDCS + Antisuppression DT (lenticular screen) •PVG (falling blocks)	•VA •Stereo acuity •CS
Verdamurthy et al., 2015a20	•N = 23 •Mean age = 39.57 ± 15.74 years •Age range = 19–62 years •Type of amblyopia: A(n = 10), S(n = 13)	•Dichoptic action VG (Unreal Tournament 2004) viewed through a stereoscope. •Duration of exposure: 40 h •Laboratory / Clinic	•Antisuppression DT (stereoscope) •PAVG (first-person shooter with Gabor patch).	•VA •Stereo-sensivity (1/arc seconds) •Gabor resolution acuity • Index for suppression (IOR): • 0 indicates complete suppression • 1 indicates no suppression
Verdamurthy et al., 2015b21	•N = 38 •Mean age = 39.7 ± 15.4 years •Age range = 19–66 years •Type of amblyopia: A(n = 16), S(n = 22)	•Dichoptic VG (n = 23) •Monocular movies with patching (n = 15) •Duration of exposure (both): 40 h, in sessions lasting 1.5–2 h, 2–5 times/week •Laboratory / Clinic (VG group/movie group) •Home (movie group)	•Antisuppression DT (stereoscope) •PAVG (first-person shooter with Gabor patch) •Monocular viewing of action movies	•VA •Stereo acuity •CS •Reading speed •Self-report of amblyopia state
Chen et al., 201622	•N = 13 (PL group) •Mean age = 18.07 ± 7.84 years •Type of amblyopia: A(n = 13) •N = 10 (Patching group, test-retest) •Mean age = 10.46 ± 3.08 years •Type of amblyopia: A(n = 10)	•Psychophysical suprathreshold binocular summation tasks within one log-unit from their cut-off spatial frequencies. •Duration of exposure: 7–12 days, 10 session/day and 70–100 trials/session (total: 5000–10,000 trials, ≈8 h) •Laboratory / Clinic	•MT •Grating contrast detection	•CS •Binocular function •Binocular phase combination •Dichoptic global motion coherence
Dadeya & Dangda, 201623	•N = 40 •Mean age: 6.03 ± 1.14 years •Type of amblyopia: A(n = 40)	•Group A (control): patching alone (n = 20) •Group B (study): play action VG along with patching (n = 20) •Duration of exposure (both): 30 min/week, 12 weeks (total: 6 h) •Laboratory / Clinic (PAVG group)	•MT •Television PAVG (car racing, Battle City, Mario) with hand-eye coordination	•VA •Stereo acuity
Herbison et al., 201624	•N = 75 •Age range: 4–8 years •Type of amblyopia: A(n = 5), S(n = 24), C(n = 46)	•I-BiTgame •I-BiT DVD •Non-I-BiT game (control group) •Duration of exposure (all): 30 min/week, 6 weeks (total: 3 h) •Laboratory / Clinic	•Antisuppression DT (interactive binocular game, I-BiT game) •PAVG (shooter game) •Antisuppression DT (interactive binocular DVD, I-BiT DVD)	•VA •Stereo acuity
Holmes et al., 201625	•N = 385 •Mean age: 8.5 ± 1.9 years •Type of amblyopia: A(n = 199), S(n = 66), C(n = 120)	•Binocular VG in iPad (n = 190) •Patching (n = 195) •Duration of exposure: VG: 1 h/day; patching: 2 h/day (both: 16 weeks) •Home	•Antisuppression DT (anaglyphic version) •PVG (falling blocks)	•VA •Stereo acuity
Kelly et al., 201626	•N = 28 •Mean age: 6.7 ± 1.4 years •Age range: 4.6–9.5 years •Type of amblyopia: A(n = 14), S(n = 9), C(n = 5)	•Binocular adventure VG iPad (Dig Rush) (n = 14) •Patching group (n = 14) •Duration of exposure (both): 2 h/day, 7 days/ week, 2 weeks (total: 28 h) •Home (both)	•Antisuppression DT (anaglyphic version) •PAVG (oriented adventure)	•VA •Stereo acuity •Suppression scotoma
Verdamurthy et al., 201627	•N = 11 •Mean age = 34.7 years •Age range = 19–56 years •Type of amblyopia: A(n = 2), S(n = 4), C(n = 5)	•Crush a dichoptic virtual insect in an area at an angle, hitting it with a manual physical cylinder •Duration of exposure: 360 trials/session, 35 sessions (8–11 weeks) •Laboratory / Clinic	•Antisuppression DT with stereocopic cues (VR) •PVG (natural visuomotor task: a ‘bug squashing’ game)	•Interocular suppression •Stereo acuity •VA •Vergence control
Barollo et al., 201728	•N = 10 •Age range = 7–53 years •Type of amblyopia: •A(n = 2), S(n = 5), C(n = 1), others (n = 2) •N = 10 (controls, non amblyopic) •Age range = 7.0–51 years	•Training in contrast detection (Gabor patch) •Duration of exposure: 21–93 sessions (16–43 weeks) •Laboratory / Clinic + Home	•MT •Grating contrast detection (Gabor patch)	•CS •AV •Foveal crowding
Bossi et al., 201729	•N = 22 •Age range = 3–11 years •Mean age: 6.6 ± 2.9 years •Type of amblyopia: A(n = 7), S(n = 6), C(n = 9)	•Viewing of dichoptic movies and gameplay wearing goggles •Group 1: A; Group 2: S + C •Duration of exposure: group 1: 8 weeks; group 2: 24 weeks (both: 1 h/day) •Home	•Antisuppression DT (shutter glasses) •Viewing movies	•VA •Stereo acuity •Interocular suppression
Singh et al., 201730	•N = 68 •Mean age: 10 ± 2 years •Type of amblyopia: A(n = 68)	•VG + occlusion (n = 34) •Duration of exposure: VG: 1 h/day, 1 month (total: 30 h); occlusion: 6 h/day, 3 months (total: 540 h) •Home •Occlusion (n = 34) •Duration of exposure: 6 h/day, 3 months (total: 540 h) •Home	•PAVG (Monocular viewing)	•VA •Stereo acuity •CS
Žiak et al., 201731	•N = 17 •Mean age = 31.2 years •Age range = 17–69 years •Type of amblyopia: A(n = 17)	•2 different DT games •Duration of exposure: 8 sessions, 20 min/game, 40 min/session (total≈5.5 h) •Laboratory / Clinic	•Antisuppression DT (VR) •PAVG (flying spaceship)+PVG (block breaker)	•VA •Stereo acuity
Gambacorta et al., 201832	•N = 21 •Age range = 7–17 years •Mean age = 9.95 ± 3.14 years •Type of amblyopia: A(n = 12), S(n = 9)	•Dichoptic VG (n = 10) •Monocular VG (n = 11) •Duration of exposure (both): 20 h •Laboratory / Clinic (both)	•Antisuppression DT (stereoscope) •PAVG (game worlds) •MT •PAVG (game worlds)	•VA •Stereo acuity
Gao et al., 201833	•N = 115 •Age range = 7–55 years •7−12 years (n = 45) 13−17 years (n = 17) ≥18 years (n = 53) •Active group (n = 56): Mean age = 22.1 ± 13.9 years •Placebo (n = 59): Mean age = 21.0 ± 13.4 years Years •Type of amblyopia: A(n = 37), S (n = 12), C(n = 61)	•Active group (n = 56) •Placebo (n = 59): same VG with full contrast (no dichoptic presentation) •Duration of exposure (both): 1 h/day, 6 weeks •Home (both)	•Antisuppression DT (anaglyphic version) •PVG (falling blocks) on iPod Touch	•VA •Stereo acuity •Interocular suppression •Quality of life questionnaire
Jia et al., 201834	•N = 19 •Mean age = 18.5 ± 1.26 years •Type of amblyopia: A(n = 19)	•MT close to its cut off spatial frequency •Duration of exposure: 630 trials/day, 6–10 days •Laboratory / Clinic	•MT •Grating contrast detection	•VA •CS •Stereo acuity •Supression
Kelly et al., 201835	•N = 41 •Mean age = 7.0 ± 1.8 years •Age range = 4.4–10.7 years •Type of amblyopia: A(n = 21), S(n = 6), C(n = 14)	•Game group: binocular adventure VG iPad (Dig Rush) (n = 20) •Duration of exposure: 1 h/day, 5 days/week, 2 weeks (total: 10 h) •Home •Movie group: watch binocular movie (n = 21) •Duration of exposure: 6 sessions, 2 weeks (total: 9 h) •Laboratory	•Antisuppression DT (anaglyphic version) •PAVG (oriented adventure) •Antisuppression DT (polarized version) •Movie viewing	•VA •Stereo acuity •Extent of suppression •Depth of suppression
Liu & Zhang, 201836	•N = 13 (who completed previous study, Zhang et al., 2014) •Mean age = 24 years •Age range = 21–29 years •Type of amblyopia: A(n = 9), S(n = 1), C(n = 3)	•Gabor stimulus. Configurations for contrast, orientation and Vernier discrimination •DT (after MT in previous study) •Duration of exposure: 2 h/session, 9 sessions (total: 18 h) •Laboratory / Clinic	•Antisuppression de-masking DT (stereoscope with Gabor patch)	•VA •Stereo acuity •CS
Manh et al., 201837	•N = 100 •Mean age: 14.3 ± 1.1 years •Type of amblyopia: A(n = 100)	•Binocular VG iPad group (n = 40) •Duration of exposure: 1 h/day (16 weeks) •Home •Patching group (n = 60) •Duration of exposure: 2 h/day (16 weeks) •Home	•Antisuppression DT (anaglyphic version) •PVG (falling blocks)	•VA
Mezad-Koursh et al., 201838	•N = 27 •Age range = 4–8 years •Mean age: 5 years •Type of amblyopia (treatment group): A(n = 7), S(n = 13), C(n = 7)	•BinoVision (training group) (n = 19) •Duration of exposure: 60 min/day, 6 days/week, 8−12 weeks (total: 48−72 h) •Sham iPad games, equal stimuli for both eyes (control) (n = 8) •Duration of exposure: 60 min/day, 6days/week, 4 weeks (total: 24 h) •Home	•Antisuppression DT (BinoVision high-tech goggles) •Viewing movies or TV programs	•VA •Stereo
Moret et al., 201839	•N = 20 •Age range = 27–58 years •Type of amblyopia: A(n = 20)	•Contrast-detection behavioural training using the lateral masking paradigm + •+ hf-tRNS (n = 10) •+ Sham stimulation (control) (n = 10) •Duration of exposure (behavioural training): 8 sessions, 45 min/session, 2 weeks (total: 6 h/3840 trials) •Duration of exposure (stimulation): 25 min (both groups) •Laboratory / Clinic	•MT •Grating contrast detection (Gabor patch)	•VA •CS
Portela et al., 201840	•N = 32 •Age range = 7–14 years •Type of amblyopia: Ani and/or strab A(n = 2), S(n = 18), C(n = 10)	•Experimental group (n = 16): initial stimulation interval depended on the value of the stereopsis at baseline. •Comparison group (n = 16): stimulation interval was constant from 840 to 750″. •Duration of exposure (both): 5 sessions/week, 12 weeks or less, 4800 responses, 60 sessions (total: 8 h) •Home (both)	•Stereopsis (Random Dot Stimuli) •PVG	•Stereo acuity
Holmes et al., 201941	•N = 138 •Mean age = 9.6 years •Age range = 7–12 years •Type of amblyopia: A(n = 66), S(n = 26), C(n = 46)	•Binocular adventure VG iPad (Dig Rush)+spectacle correction (n = 69) •Spectacle correction alone (control) (n = 69) •Duration of exposure (both): 1 h/day, 5 days/week, 8 weeks (total: 40 h) •Home (both)	•Antisuppression DT (anaglyphic version) •PAVG (oriented adventure)	•VA •Stereo acuity •Cover test
Law & Backus 201942	•N = 19 •Mean age = 27.9 years •Age range = 16–50 years •Type of amblyopia: A(n = 17), C(n = 2)	•Mixed-contrast (n = 9): higher contrast to the amblyopic eye. •Fixed-contrast (n = 10): contrast was the same in both eyes. •Duration of exposure (both): 10 weeks, 45′/session, 10 sessions, 160 trials/session (total: 1600 trials, ~7.5 h) •Laboratory / Clinic (both)	•Antisuppression DT with stereocopic cues (stereoscope)	•Composite stereodepth (CSD) score: mapped stereoacuity thresholds and percent correct on highdisparity trials onto a single range of 0–20. Scores from 0 to 13.3 are given over to stereoacuity values, and scores from 13.3–20 are given over to percent correct.
Liu & Zhang, 201943	•N = 11 •Mean age = 23 years •Age range = 19–28 years •Type of amblyopia: A (n = 8), C(n = 3)	•Gabor stimulus. Configurations for contrast and orientation discrimination •Group 1 (n = 6): contrast training and then orientation exposure; Group 2 (n = 5): orientation exposure and then contrast training •A subset of participants (n = 6) then performed orientation MT (9 sesions). •Duration of exposure (DT): 2 h/session; 800~1000 trials/session (5 sessions; total: 10 h) •Duration of exposure (MT): 2 h/session; 800~1000 trials/session (9 sessions; total: 18 h) •Laboratory / Clinic (both)	•Antisuppression de-masking‡ DT (stereoscope with Gabor patch) •Antisuppression DT (stereoscope with Gabor patch) + MT •‡ discounting the masking effect from a noise masker presented to the fellow-eye	•VA •Stereo acuity •CS
Sauvan et al., 201944	•N = 17 •Mean age = 34 years •Age range = 9–67 years •Type of amblyopia: A (n = 11), S( n = 2), C(n = 4)	•DT or nonpatched group (n = 10) •Patched group (n = 7) (patching over AE two hours prior to each DT) •Duration of exposure (both): 6 sessions, 1.5 h/sesión (total: 9 h) •Laboratory / Clinic (both)	•Antisuppression DT (polarized version) •Movie viewing	•VA •Stereo acuity •Interocular suppression
Birch et al., 202045	•N = 48 •Mean age = 6.8 ± 1.8 years •Age range = 4.3–10.8 years •Type of amblyopia: A (n = 27), S + C(n = 21)	•Game group: binocular adventure VG iPad (Dig Rush) (n = 24) •Duration of exposure: 1 h/day, 5 days/week, 2 weeks (total: 10 h) •Home •Patching group (n = 24) •Duration of exposure: 2 h/day, 7 days/week, 2 weeks (total: 28 h) •Home	•Antisuppression DT (anaglyphic version) •PAVG (oriented adventure)	•VA •Stereo acuity •Extent of suppression
Gu et al., 202046	•N = 46 •Mean age = 15.9 ± 4.0 years •Age range = 12–25 years •Type of amblyopia: A (n = 46) •N = 12 •Mean age = 24.4 ± 3.2 years •Age range = 21–30 years •Normal vision	•MT + patching (n = 27) •Duration of exposure: MT: 10 sessions/day, 70~100 trials/sessions, 7–14 days (total: 5,000−10,000 trials, 8 h); patching: 2 h/days, 7−14 days. •Laboratory / Clinic •Patching group (n = 5) •Duration of exposure: patching: 2 h/day, 10−13 days •Home	•MT •Grating contrast detection ( Gabor patch)	•VA •CSF •Stereo acuity •Interocular balance •SSVEPs

Note: A: anisometropic amblyopia; AE: amblyopic eye; BiT: binocular treatment; C: combined mechanism amblyopia (i.e., strabismic and anisometropic); cpd: cycles per degree; CS: contrast sensitivity; DT: dichoptic therapy; h: hour/ hours; hf-tRNS: high-frequency transcranial random noise stimulation; I: isometropic; IOR: interocular ratio; min: minutes; MT: monocular training; PL: perceptual learning; S: strabismic amblyopia; SSVEPs: Steady-state visually evoked potentials; tDCS: transcranial direct current stimulation; VA: visual acuity; VG: video game; VR: virtual reality. "Both" refers applied equally to both groups.