Amblyopia is the most common cause of visual impairment in children. It occurs when there is a misalignment between what the two eyes see, such as when one eye is clouded by a cataract, when there is a refractive error, or when the eyes are positioned at different angles. The brain has a slight preference for the more functional eye at first, but as that eye continues to send useful information to the brain, the brain’s preference for that eye grows stronger at the expense of the other.
Traditional approaches to treatment
Patching vs cycloplegics has been the cornerstone of amblyopic treatment for hundreds of years. Because a patch is simple to apply and cost-effective treatment, patching therapy is usually the first-line procedure. However, there are numerous flaws since the psychological and social consequences of wearing a patch might generate problems with compliance. Patching therapy has been challenging for parents to stick to due to the inadequacies and discomfort of reducing a child’s viewing field via the patch. Even when visual acuity improves in the amblyopic eye, studies reveal that binocular vision is underutilized. Binocular vision occurs when the visual fields of both eyes overlap, allowing for better depth perception.
The idea of binocular vision in amblyopia is important to recognize because the amblyopic eye usage is forced with a patch, thus increasing its visual potential; however, because the opposing eye is patched, the 2 eyes do not develop in synchrony. Ultimately, while patching therapy has had some success, there is a clear need for more effective alternatives.
Atropine eye drops have been used as an alternative to patching. Atropine inhibits muscarinic receptors in the eye, which control the size and shape of the pupil and lens. Atropine has a mydriatic (increased pupil size) and cycloplegic (paralysis of the fibers controlling lens accommodation) effect, which acts as a blurring therapy for the well-seeing eye. Atropine eye drops were found to be equally effective as patching for moderate amblyopia; however, given the ease of applying an eye patch versus the inconvenience of putting in drops that cause a strange blurring sensation, it’s no surprise that patching therapy is preferred by both parents and practitioners.
A novel approach to treatment: binocular treatment
Despite the fact that amblyopia is a binocular problem that has been recognized for many years, the traditional approach has always focused on monocular vision. Binocular approaches to amblyopic vision have only recently been explored. In the recent amblyopic literature, suggestions for novel therapeutic approaches have made significant progress. Pure monocular therapy, pure binocular therapy, and a combination therapy consisting of both are among the approaches discussed. While we’ve already discussed monocular approaches, we’ll now turn our attention to binocular approaches.
A new treatment regimen, using dichoptic glasses while playing video games, incorporates a binocular stimulation that was previously missing in amblyopic treatment methodologies. This dichoptic manipulation of different contrasts allows both eyes to be stimulated. By presenting a high-contrast image to the amblyopic eye, the method trains the eyes. This method is distinguished by the fact that it does not aim to suppress the fixing eye, but rather to strengthen neural connections in the amblyopic eye, thereby promoting binocular vision.
Numerous clinical trials have shown that binocular game treatment is more effective than patching as a treatment for amblyopia. Game therapy is less time-consuming than patching and results in better best-corrected visual acuity. When discussing binocular treatment, clinical suppression must be assessed. Under binocular viewing conditions, clinical suppression refers to the absence of an amblyopic and/or strabismic eye’s contribution. Until recently, there was no gold standard for determining the degree of clinical suppression. According to recent research, the strength of suppression and the degree of amblyopia present have a direct relationship.
There has been a noticeable shift in amblyopic literature in recent years, away from the previous trend of monocular suppression therapy. Binocular therapy has an additional benefit of increased stereopsis in addition to improved visual acuity. Although it was previously believed that adults with amblyopia should not be treated, new research has contradicted this belief, indicating that there may be some benefit to treating amblyopic adults. Many previously held beliefs about amblyopia are being challenged, and as research trials continue to demonstrate the efficacy of dichoptic therapy, it may soon become the gold standard of care.
Source: Mufti, O., & Ramasubramanian, A. (2019). Binocular Treatment for Amblyopia. Advances in Ophthalmology and Optometry, 4, 65–73. https://doi.org/10.1016/j.yaoo.2019.04.003