Key points

Introduction

Amblyopia is the most common cause of monocular vision loss in children, with a prevalence of 2% to 4% [ ]. The condition is characterized by decreased vision in one or both eyes due to abnormal visual development during the critical period, the first 8 to 10 years of life. Amblyopia occurs when the normal visual input to one or both eyes is disrupted; this can be secondary to significant refractive errors, strabismus, or deprivation of vision such as in congenital ptosis and cataracts, or a combination of these [ ]. Untreated amblyopia has a significant life-long impact because it can affect fine motor skills [ ] and can cause reduced reading speed in children [ ], whereas in adults, it can affect the quality of life, leading to reduced employment opportunities and lower self-esteem [ ].

The basis of amblyopia treatment has been to correct the underlying cause, such as refractive errors, and to encourage the use of the amblyopic eye by limiting the use of the dominant eye. Traditionally, this has been achieved by patching, using Bangerter filters, or pharmacologically penalizing the dominant eye with atropine eye drops. These treatments have demonstrated similar efficacy in improving vision in the amblyopic eye; however, treatments can be limited by poor adherence [ ] and social stigma [ ]. Conventional amblyopia success rates are still less than ideal, and binocular outcomes often are poor regardless of the improved amblyopic eye acuity [ ]. Interestingly, there are patients with prolonged and good adherence to treatment who still may not fully improve, suggesting other underlying limitations of suppression treatments [ ].

Recently, a new, binocular approach to amblyopia treatment has been introduced. In this article, we will review the basis of binocular amblyopia treatment, major research studies evaluating its efficacy and limitations, and the current status of available binocular treatments.

Significance and relevant background research

The dichoptic binocular therapy was initially introduced by Baker and colleagues [ ], who showed that binocular summation of contrast remains intact in strabismic amblyopia, suggesting that amblyopia is an intrinsic binocular problem [ ]. Further research by Hess and group [ , ] demonstrated that binocular treatments have the potential not only to improve vision in the amblyopic eye but also to improve binocular function, stereopsis, and fusion. Various strategies utilizing a binocular approach for the treatment of children and adults with amblyopia have been proposed, including interactive versions such as playing video games [ , ] or watching movies [ , ]. These methods seem to be more attractive to children and parents and may improve treatment adherence. However, it is essential to evaluate the efficacy and indications of binocular treatment carefully.

Hess and colleagues [ ] introduced one of the most promising therapies for binocular amblyopia treatment. The dichoptic or antisuppression training is characterized by presenting a normal-contrast image to the amblyopic eye and a low-contrast image to the fellow eye. The concept is based on findings by Mansouri and colleagues [ ], which showed that for different tasks, such as motion and orientation, when the signal to the fellow fixing eye is reduced in strength, strabismic amblyopes could exhibit balanced interocular performance and combined information between their 2 eyes, as normal individuals do. Further research confirmed the author’s prior findings, showing that when both eyes are stimulated with different contrast stimuli in each eye, the combined information leads to strengthening of binocular vision, and, importantly, the results were obtained in amblyopic children and adults [ , ].

Following the positive findings of the dichoptic amblyopia treatment, further studies with promising results were published by different research teams. Knox and colleagues [ ] and Mansouri and colleagues [ ] published a prospective case series showing significant improvement in visual acuity in amblyopic children treated using a dichoptic approach with video goggles. In 2013, Li and colleagues [ ] compared monocular and dichoptic training in a crossover controlled study including only adults and found binocular training, using the falling blocks game on video goggles, resulted in significantly better improvements in visual acuity and stereopsis than monocular training using the same game. Li and colleagues evaluated children aged 4 to 12 years using anaglyphic glasses to play binocular games on an iPad platform and found that binocular treatment provided rapid improvement in visual acuity, with a stable visual acuity for at least 3 months following cessation of treatment [ ]. In another study, when sham games were compared with binocular games in younger children, aged 3 to 6.9 years, binocular therapy was found to be more effective than sham therapy in treating amblyopia, although stereoacuity did not significantly improve in the binocular group [ ].

Importantly, binocular amblyopia treatment is not limited to dichoptic training. Other strategies, including balanced binocular viewing and interactive binocular treatment (I-BiT), have been considered even before the dichoptic approach. The balanced binocular viewing approach is based on using a Gaussian blur to degrade the image seen in the nonamblyopic eye, balancing the content received between the 2 eyes [ ]. The I-BiT approach combines games and movie clips visualization using binocular technology. The patient uses a shutter glasses system that presents different parts of a 2-dimensional image to either eye, with the additional task of combining the 2 images and an “enriched” image to be presented only to the amblyopic eye [ ].

These approaches have brought a new perspective to the treatment of amblyopia. To answer the fundamental question of whether the improvement in visual acuity and the sensory benefits of this novel treatment were equivalent to the traditional treatment of patching, further research, in the form of randomized clinical trials (RCTs), was necessary. The results of 16 RCTs with more than 20 subjects, available on PubMed from 2016 to 2023, are summarized in Table 1 .

Table 1

Randomized control trials with more than 20 subjects evaluating the efficacy of the binocular amblyopia treatment from 2016 up to 2023

Author, year	Study design, level of evidence	Total patients	Age range (years)	Causes of amblyopia	Treatment	Treatment duration	Outcomes	Conclusions
Herbison et al, [ ] 2016	RCT Binocular treatment vs sham games	75	4–8 y	• S (24) • A (5) • A/S (36)	• I-BiT game 1 h/d for 6 wk vs • I-BiT video or non-I-BiT sham game	10 wk TTo Final follow-up 4 wk after end of the treatment	Difference in improvement of VA	No significant difference between the treatments P = .429
Holmes et al, [ ] 2016	RCT Binocular treatment vs patching	385	5–12 y	• A (199) • S (66) • A/S (120)	• Dichoptic iPad game for 1 h/d vs • Patching 2 h/d	16 wk	Difference in improvement of VA	The noninferiority analysis was indeterminate.
Kelly et al, [ ] 2016	RCT Binocular Treatment vs patching	28	4.9–9.5 y	• S (9) • A (14) • A/S (5)	• Dichoptic game (Dig Rush) for 1 h/d for 5 d/wk vs • Patching 2 h/d	2 wk	Difference in improvement of VA	The binocular iPad game was more efficacious than patching at the 2-wk visit P = .02
Rajavi et al, [ ] 2016	RCT Binocular treatment vs patching	50	3–10 y	• A (50)	• I-BiT game 20 min/session for 5 sessions/wk vs • Patching 2 h/d	4 wk	Difference in improvement of VA	1 mo after cessation of I-BiT, there was no significant difference in VA between the 2 groups
Manh et al, [ ] 2018	RCT Binocular treatment vs patching	100	13–17 y	• A (51) • S (14) • A/S (35)	• Dichoptic falling blocks game for 1 h/d vs • Patching 2 h/d	16 wk	Difference in improvement of VA	1 y after the cessation of treatment there was no significant difference in VA between group treatments
Gao et al, [ ] 2018	RCT Binocular treatment vs sham games	115	7–55 y	• A (42) • S (12) • A/S (61)	• Dichoptic game on iPad) for 1 h/d for 6 wk vs • Sham video game	10 wk Final follow-up 4 wk after end of the treatment	Difference in improvement of VA	No significant difference between the treatment P = .25
Holmes et al, [ ] 2019	RCT Binocular treatment vs optical treatment	138	7–12 y	• A (66) • S (34) • A/S (38)	• Dichoptic game on iPad for 1 h/d, per 6 wk vs • Spectacles only	8 wk	Difference in improvement of VA	No significant difference between the treatment groups, P = .71
Rajavi et al, [ ] 2021	RCT Binocular treatment vs patching	50	4–10 y	• A (12) • S (18)	• Dichoptic virtual reality game through a headset for 1 h/d per 5 d vs • Patching 2,4, and 6 h depending on baseline VA	4 wk	Difference in improvement of VA	No significant difference between the treatment groups, P = .59
Pang et al, [ ] 2021	RCT Binocular treatment vs placebo	23	8–46 y	• A (18) • S (2) • A/S (3)	• Dichoptic game on iPod for 1 h/d vs • Placebo, identical game but no dichoptic	6 wk Final follow-ups at 6 wk and 18 wk after end of the treatment	Difference in improvement of VA and Titmus stereo acuity	Significant improvement in VA and Titmus stereo acuity in the TTo group compared with the placebo group
Elhusseiny et al, [ ] 2021	RCT Binocular treatment vs sham	20	7–38 y	• A (10) • S (3) • A/S (7)	• Dichoptic movies, tv shows or cartoons on smartphone, and a virtual reality headset for 1 h/d, 6 d/wk for 8 wk vs • Sham group for 4 wk and dichoptic treatment of 4 wk (sham-crossover group	8 wk Final follow-up at 16 wk	Difference in improvement of VA and stereo acuity	There was no significant improvement in VA in either group. There was a significant improvement in stereoacuity in the sham-crossover group but not in the full-treatment group
Xiao et al, [ ] 2022	RCT Binocular treatment + refractive correction vs refractive treatment	105	4–7 y	• A (59) • S (17) • A/S (28)	• Dichoptic movie or show on smartphone and a virtual reality headset for 1 h/d, 6 d/wk plus full-time refractive correction for 12 wk vs • Refractive correction only	12 wk	Difference in improvement of VA and safety	Statistically significant greater improvement in the binocular treatment group compared with the refractive correction alone ( P = .0011). No serious adverse events were reported
Manny et al, [ ] 2022	RCT Binocular treatment + optical correction vs optical treatment	182	4–6 y	• A (61) • S (15) • A/S (16)	• Dichoptic game on iPad for 1 h/d, 5 d/wk for 8 wk vs • Spectacles only (at least 16 wk of wear)	Primary outcome at 4 wk and secondary outcome at 8 wk	Difference in improvement of VA	Binocular treatment resulted in significant greater improvement in amblyopic-eye VA over 4 wk ( P = .03) but not 8 wk
Jost et al, [ ] 2022	RCT Binocular TTo vs patching	65	3–7 y	• A (19) • S (29) • A/S (12)	• Dichoptic animated movie 4.5 h/wk vs • Patching: 2 h/d 7 d a wk	2 wk	Difference in improvement of VA	No significant difference between the treatment groups, P = .48.
Wygnanski-Jaffe et al, [ ] 2023	RCT Binocular TTo vs Part time patching	103	4–8 y	• A (95) • S (8)	• Binocular eye-tracking-based home 90 min/d, 5 d/wk vs • Patching: 2 h/d 7 d a week	16 wk	Difference in improvement of VA	The binocular treatment was noninferior to patching and there was no significant difference in improvement in VA and stereoacuity The binocular treatment group had a significantly higher adherence than the patching group
Zhu et al, [ ] 2023	RCT Binocular 3D TTo (combined) + patching vs part time patching alone	32	5–12 y	• A (24) • S (8)	• 3D movie 1–1.5 h/session, at least twice a week. Total of 30 h within 6 wk vs • 2–6 h/d patching depending on VA	6 wk	Difference in improvement of VA and stereo acuity	The combined group had greater significant improvement of VA compared with the patching group and had significantly improvement of stereoacuity
Roy et al. 2023	RCT Binocular TTo vs patching	55	5–15 y	• A (55)	• Dichoptic video game with adjusted contrast for 2 h/d vs • 6 h/d patching	3 mo	Difference in improvement of VA and stereo acuity	There was no significant difference in distance and near vision between the 2 groups, but there was a better significant improvement in near steropaucity and contrast sensitivity

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Recent Advances in Eyelid Tumors
2. Visual Snow Syndrome
3. Pharmacologic Treatment of Presbyopia
4. The Use of Therapeutic Microprism for Patients with Post-concussion Syndrome

Stay updated, free articles. Join our Telegram channel

Join