Heena Gupta, Bachelor of Optometry

Paediatric Fellow, Dr. Shroff’s Charity Eye Hospital, Delhi, India

Introduction: Amblyopia is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experiences in the early life. For example, Strabismus, Anisometropia, Form deprivation. ⁽¹⁾ The period through which the visual system can be affected by environmental manipulation is referred to as a critical or sensitive period that is up to 7-8 years of age. ⁽²⁾ The neuronal circuits stabilise during this critical period with no change occurring beyond the age indicating that amblyopia cannot be treated after the age of 7 years. ⁽³⁾

Causes: There are three types of Amblyopia, based on the underlying causes: –

1. Strabismic Amblyopia: It causes inhibition of received stimuli integration. Distortion of vision interferes with numerous visual tasks including visual acuity and alignment In strabismus, the different stimuli received by the eyes prevent fusion, binocular vision & altered stereopsis. Treatment:- Vision therapy, eye patching, eye drops, strabismic surgery. ⁽⁴⁾
2. Refractive Amblyopia: Amblyopia can be caused by significant anisometropic or bilateral refractive error.
3. Deprivation Amblyopia: – It is associated with the conditions such as cataract, corneal opacities, vitreous opacity, or ptosis occurring in early life. ⁽⁵⁾

Treatment: Refractive correction, penalization, patching of the better seeing eye are the most used treatment modalities for treating amblyopia.

Patching or Occlusion therapy: Occlusion of the better eye and forcing the amblyopic eye to work proved to significantly improve the visual acuity but had poor compliances. ⁽⁶⁾ because difficulty of forcing a patient to wear the patch. ⁽⁷⁾ Instead of providing time consuming treatment like patching, therapies like perceptual learning or video games are gaining popularity in current amblyopia therapy. These methods demand significant patient’s attention throughout the time of therapy. ⁽⁸⁾

Penalisation: The principle is to force the amblyopic eye to a greater use for distance, near or both with the help of glasses or cycloplegic drugs. It is done by administering Atropine sulfate (1%) into the sound eye of a child with amblyopia. The alternative of pharmacological agents is by using spectacle correction to produce blurring of the better eye’s vision either at distance or nearby, this is known as Optical penalisation. With the help of Video games, Amblyopia was treated binocularly & showed better compliance with improvement in both visual and stereo -acuity which was followed by Dichoptic having a significant successful rate over the years. ^(9,10)

Dichoptic: 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 amblyopia who don’t respond to patching. Another  advancement of the dichoptic technique is that visual acuity gained through this method is maintained for at least 12 months . ^(9,10)

Bynocs: Bynocs is comprehensive cloud-based software for binocular vision assessment & therapy. It also evaluates other sensory visual functions like contrast sensitivity, color vision, fixation pattern, suppression, and diplopia.

I-BIT: Also known as Interactive binocular treatment system which is used to treat amblyopia using dichoptic stimuli presented via virtual reality game play or movie watching.

Mfbf technique [monocular fixation in a binocular field]: This technique involves the presentation of peripheral stimuli to both the eyes, while only the amblyopic eye is stimulated at the fovea. For e.gThe patient may be instructed to complete tasks such as crossword puzzles, or placing dots in the ‘O’ letters in a text, using a pen and wearing red-green glasses, with the red lens of the non- amblyopic eye.

References:

1. Wang J. Compliance and patching and atropine amblyopia treatments. Vision research. 2015 Sep 1;114:31- 40. https://doi.org/10.1016/j.visres.2015.02.012
2. Daw NW. Critical periods and amblyopia. Archives of ophthalmology. 1998 Apr 1;116(4):502-5. https://doi.org/10.1001/archopht.116.4.502
3. Sengpiel F. Plasticity of the visual cortex and treatment of amblyopia. Current Biology. 2014 Sep 22;24(18):R936-40. https://doi.org/10.1016/j.cub.2014.05.063
4. Van de Graaf ES, Van der Sterre GW, Polling JR, Van Kempen H, Simonsz B, Simonsz HJ. Amblyopia & Strabismus Questionnaire: design and initial validation. Strabismus. 2004 Jan 1;12(3):181-93. doi:1080/09273970490491106
5. Varma R, Deneen J, Cotter S, Paz SH, Azen SP, Tarczy-Hornoch K, Zhao P, Study Group TM. The multi-ethnic pediatric eye disease study: design and methods. Ophthalmic epidemiology. 2006 Jan 1;13(4):253-62.
6. Searle A, Norman P, Harrad R, Vedhara K. Psychosocial and clinical determinants of compliance with occlusion therapy for amblyopic children. Eye. 2002 Mar;16(2):150-5.
7. Holmes JM, Beck RW, Kraker RT, Cole SR, Repka MX, Birch EE, Felius J, Christiansen SP, Coats DK, Kulp MT. Impact of patching and atropine treatment on the child and family in the amblyopia treatment study. Archives of ophthalmology (Chicago, Ill.: 1960). 2003 Nov 1;121(11):1625-32. https://doi.org/10.1001/archopht.121.11.1625
8. Repka MX, Beck RW, Holmes JM, Birch EE, Chandler DL, Cotter SA, Hertle RW, Kraker RT, Moke PS, Quinn GE, Scheiman MM. A randomized trial of patching regimens for treatment of moderate amblyopia in children. Archives of ophthalmology (Chicago, Ill.: 1960). 2003 May 1;121(5):603-11.
9. Li SL, Reynaud A, Hess RF, Wang YZ, Jost RM, Morale SE, De La Cruz A, Dao L, Stager Jr D, Birch EE. Dichoptic movie viewing treats childhood amblyopia. Journal of American Association for Pediatric Ophthalmology and Strabismus. 2015 Oct 1;19(5):401-5.
10. Hess RF, Mansouri B, Thompson B. Restoration of binocular vision in amblyopia. Strabismus. 2011 Sep 1;19(3):110-8. https://doi.org/10.3109/09273972.2011.600418