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Amblyopia Management – What’s New?

by | Oct 1, 2020 | Manuscripts | 0 comments

Bhumin Parekh, Bachelor of Optometry

Binocular Vision Fellow, Sankara Nethralaya

 

Introduction:

Amblyopia is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experience early in life (e.g. strabismus, anisometropia, or form deprivation) (1). Although providing accurate optical correction can treat about 25% of children with amblyopia, the dominant approach to amblyopia treatment includes strategies to enhance visual input from the amblyopic eye (relative to the fellow eye) which can only be achieved by interventions that degrade visual input to the fellow eye (2).

Critical Period and Neuroplasticity:

The human visual system is not fully developed at birth which undergoes maturation over the first several years of life. To do so it must be exposed to normal visual environments. Consequences arise when this environment is disrupted. The period through which the visual system can be affected by environmental manipulation is referred to as the critical or sensitive period that is up to 7-8 years of age (3). It was thought that the neuronal circuits stabilize during this critical period with no change occurring beyond that age indicating that amblyopia cannot be treated after the age of 7 years (4). Recent researches suggest that the adult human visual cortex had a significant degree of plasticity that can be enhanced or restored in later life (5).

Visual function deficits in amblyopia:

Although the loss of visual acuity is the most common visual deficit in amblyopes, it also includes deficits in contrast sensitivity, high level of spatial uncertainty, spatial distortion, impaired reading abilities, crowding, ocular motility, accommodation, attention, fixation, motion perception, and temporal processing” (2)(6)(7)(8). Early detection is the key in preventing the long-term effects of amblyopia (1).

Treatment (Refer Figure 1):

The gold standard treatments in amblyopia are refractive correction and penalization or patching of the better eye and forcing the amblyopic eye to work which showed significant improvement in visual acuity but had poor compliance (9).

 

Compliance is poor because of the social and psychological difficulty of forcing a patient to wear a patch (10). Instead of providing a passive and time-consuming treatment like patching, therapies like perceptual learning or video games should be provided that demand their attention throughout the time of therapy. With the help of video games, amblyopia was treated binocularly and showed better compliance with improvement in both visual acuity and stereo-acuity which was then followed by dichoptics that had a significant success rate over the years.

Figure 2: Example of a dichoptic based virtual reality spaceship game seen through the head mounted display. Spaceship is seen only with the dominant eye, the left part of the figure. The amblyopic eye views the right half of the screen which the patient sees the gates of different contrast in order to flight spaceship through them by head movement. Patient can avoid obstacles by firing at them with the help of remote controller. (Image Consent: Author consented for using the picture for any education purpose)

 

Dichoptic games provide contrast-balanced binocular vision with low contrast for the fellow eye and high contrast for the amblyopic eye and can even treat adult amblyopes who don’t respond to patching. Another important advancement of the dichoptics technique is that visual acuity gained through this method is maintained for at least 12 months (11)(12). Now the world is moving towards the virtual reality era for training amblyopia (6).Combination of dichoptics and virtual reality and other treatment modalities can maximize the improvements due to its gaming paradigm and will help the clinicians to provide a clear idea, regarding the prognosis, to the amblyopic patients with maximum compliance (Refer Figure 2).

 

References:

  1. Wang, J. (2015). Compliance and patching and atropine amblyopia treatments. Vision research, 114, 31-40.
  2. Nguyen, J., & Levi, D. M. (2011). Video-game play induces plasticity in the visual system of adults with amblyopia. PLoS biology, 9(8), e1001135.
  3. Daw, N. W. (1998). Critical periods and amblyopia. Archives of ophthalmology, 116(4), 502-505.
  4. Sengpiel, F. (2014). Plasticity of the visual cortex and treatment of amblyopia. Current Biology, 24(18), R936-R940.
  5. Castaldi, E., Lunghi, C., &Morrone, M. C. (2020). Neuroplasticity in adult human visual cortex. Neuroscience &Biobehavioral Reviews.
  6. Irfan, S., Adil, N., &Iqbal, H. (2013). Determining the efficacy of full-time occlusion therapy in severe amblyopia at different ages. F1000Research
  7. Polat, U., Ma-Naim, T., &Spierer, A. (2009). Treatment of children with amblyopia by perceptual learning. Vision research, 49(21), 2599-2603.
  8. Li, S. L., Reynaud et al. (2015) Dichoptic movie viewing treats childhood amblyopia. Journal of American Association for Pediatric Ophthalmology and Strabismus, 19(5), 401-405.
  9. Searle, A., Norman, P., Harrad, R., &Vedhara, K. (2002). Psychosocial and clinical determinants of compliance with occlusion therapy for amblyopic children. Eye, 16(2), 150.
  10. Holmes, J. M., Beck et al. (2003). Impact of patching and atropine treatment on the child and family in the amblyopia treatment study. Archives of ophthalmology (Chicago, Ill.: 1960), 121(11), 1625-1632.
  11. Hess, R. F., Mansouri, B., & Thompson, B. (2011). Restoration of binocular vision in amblyopia. Strabismus, 19(3), 110-118.
  12. Li, S. L., Reynaud et al. (2015). Dichoptic movie viewing treats childhood amblyopia. Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS}, 19(5), 401-405.

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