Amblyopia is a condition in which a person has a “weak” eye; one of the eyes has reduced vision. More commonly referred to as a “lazy eye”, amblyopia is usually diagnosed and treated in childhood. Amblyopia is typically caused by refractive errors, like nearsightedness (myopia) or farsightedness (hyperopia), but can also be caused by other eye issues, such as a strabismus (crossed or wandering eye) (Wong, 2014). When children are young, tracking issues as toddlers or regular well-child check-ups using visual screening charts will typically reveal the amblyopia, as there may be no outward indications of the issue if a strabismus is not present (Wong, 2014).
Fig. 1: Types of strabismus Fig. 2: Example of vision chart
From a clinical standpoint, amblyopia is diagnosed when the affected eye has a visual acuity of 20/40 or worse, and there is a difference in vision between the eyes of two or more lines on a vision screening chart (Wong, 2014). This means that the affected eye has much poorer vision than the unaffected eye. In addition to refractive issues or strabismus, amblyopia may also be caused by competitive or inhibitory nervous pathways; if these visual pathways are not stimulated properly, the brain will start to “favor” the strong eye, causing the affected eye to continue weakening (Wong, 2014).
Once diagnosed, amblyopia is typically treated by “penalization” of the strong eye; the strong eye is covered by a patch (occlusion therapy) for a few hours a day to strengthen the affected eye (Webb, et al., 2006). However, in an article from the British Journal of Ophthalmology, the authors present two issues with the current treatment of amblyopia; firstly, there is no effective alternative to occlusion therapy, and secondly, there is “considerable slippage” of visual acuity once occlusion therapy is stopped (Webb, et al., 2006). The authors propose an alternative treatment to occlusion therapy for adults with amblyopia, one that promises significant long-term improvements in visual acuity: visual perceptual learning.
Visual perceptual learning is described as “improvements in the function of brain networks that integrate processes including sensory representations, decision, attention, and reward and balance plasticity with system stability” (Dosher & Lu, 2017). Plainly speaking, visual perceptual learning is based on the theory of plasticity in the visual cortex, meaning that these pathways can be “retrained” to overcome the issues of amblyopia and eventually restore normal visual acuity. Visual perceptual learning devises multiple tasks that relate to specific functions of visual acuity, such as motion detection, contrast differentiation, and orientation discrimination (Dosher & Lu, 2017). Feedback and/or rewards are offered, and further tasks aim to not only continue improving visual acuity, but to reinforce those tasks already completed (Dosher & Lu, 2017). One very convenient and accessible method for visual perceptual learning: video games!
References
Dosher, B., & Lu, Z.-L. (2017, July 19). Visual Perceptual Learning and Models. Annual Review of Vision Science, 3. 10.1146/annurev-vision-102016-061249
Webb, B., McGraw, P., & Levi, D. (2006, March 17). Learning with a lazy eye: a potential treatment for amblyopia. British Journal of Ophthalmology, 90(4). https://bjo.bmj.com/content/90/4/518.full
Wong, A. M. (2014, March 4). Amblyopia (lazy eye) in children. Canadian Medical Association Journal, 186(4). 10.1503/cmaj.130666
Hi! Awesome post. I had a lazy eye as a kid and actually underwent the very occlusion therapy you discuss above. I have to say, it worked for me! Of course, I am just one case in millions. I never played video games, but I can see how that would help. Have they seen cases where the lazy eye comes back after years of being dormant (for lack of a better term), or is the "slipping" a pretty immediate response after therapy is stopped?
ReplyDeleteHi Molly! Occlusion therapy is the gold standard, and from what I understand, it works very well for most people. From the research I did, it seems as though the slippage can either be an immediate response, or it can return gradually; this is perhaps one of the reasons we still see adults with amblyopia. The visual perceptual learning models employing video games for treatment of amblyopia were largely directed at adults; this could be an effective method if the slippage from childhood occlusion therapy lead to a recurrence of the amblyopia in adulthood.
ReplyDeleteFantastic post! I always enjoy your images. I was shocked to see that the treatment of using eyepatch has received critique. I know my aunt had to use an eyepatch for this issue as a child, and my little cousin had this as a baby and they made her use an eyepatch as well, and that was not too long ago. When I looked up alternative treatments, I also found that there has been success in the administration of atropine, an involuntary nervous system blocker, for children who did not have success with patch therapy. I wonder if this treatment alongside the visual perception learning could increase positive results. Again, great post!
ReplyDeleteSeol, B. R., Yu, Y. S., & Kim, S. J. (2017). Effect of 4-Month Intermittent Atropine Penalization in Amblyopic Children for Whom Patch Therapy Had Failed. Journal of pediatric ophthalmology and strabismus, 54(6), 375–380. https://doi.org/10.3928/01913913-20170329-02