MeSH Heading(s)

amblyopia, flicker fusion


Background: Gold standard penalization therapies for amblyopia are thankfully being challenged by new techniques and new technologies. One such technology, rapid alternate occlusion or alternating flicker was recently studied and improved visual acuity and stereopsis in anisometropic amblyopes.

Methods: Starting with a recapitulation of the Eyetronix Flicker Glass Clinical Study of the affect of 7Hz square-wave alternating flicker on anisometropic amblyopia, further analysis looks at how stereopsis changed through the period of the study, and possible age-related differences in outcomes and changes in reading symptomology pre- to post-therapy. A discussion of the complexity of how alternating flicker may work therapeutically is presented separately in an appendix.

Results: In a group of 23 anisometropic amblyopes, 12 weeks of Eyetronix Flicker Glass therapy improved BCVA of the amblyopic eye about two lines with no adverse effects to the better eye with considerably less therapy time than in penalization techniques, improved both random dot “global” and contoured “local” stereopsis and also reduced symproms of reading problems. Age and beginning acuity were non-factors in success of the therapy.

Conclusions: Paradoxically, square-wave rapidly alternating visual flicker may present one of the few truly bilateral therapeutic visual stimuli to the cortex. The mechanism may include the anti-masking effect of appropriately-timed on- and offset of the flickering visual stimuli, flicker as a strong visual motion stimulus driving visibility at or near the LGN, and temporal summation.

Human Subject Research (HSR) Review Status

IRB review/approval required and obtained

IRB/Ethics Committee Protocol or Proposal Number


Competing Interests

The author has no financial ties to Eyetronix, but is on the advisory board for Eyetronix, Incorporated. The author does hold the original patent on rapid alternation with liquid crystal lenses, US patent #5,264,877; that patent has expired and has no relationship to Eyetronix Flicker Glass.



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