Can several days of complete darkness cure lazy eye?

It might. Here's why.

 Backus and Williams after 5 days of Binocular Deprivation in 2012

Backus and Williams after 5 days of Binocular Deprivation in 2012

so what is amblyopia?

Amblyopia, sometimes called lazy eye (and literally meaning "blunt vision") is a common visual disorder that affects 4% of people in the USA, in which a person has poor vision in one eye. The poor vision—which can range from slightly degraded vision to almost complete blindness—cannot be fixed with corrective lenses because the deficit involves changes in the vision centers of the brain. Typically amblyopia develops during early childhood when the brain forms poor connections to one eye. 

There are three types of amblyopia:

  • Refractive - this results when there is a difference in focusing ability between the two eyes at an early age. One eye being blurry prevents the brain from learning how to see accurately with that eye.
  • Strabismic - this is an asymmetry of vision due to 'eye-turn'. Many people confuse strabismus with amblyopia. While some people with amblyopia have strabismus, not everyone with strabismus has amblyopia.
  • Deprivation - also called 'occlusion amblyopia', this results when one eye is obstructed at an early age by a cataract or other occluder. 

We're investigating whether darkness can improve treatment for Refractive (anisometropic) amblyopia. If effective, there could also be implications for the treatment of Strabismic and Deprivation amblyopia, as well as visual deficits from stroke or other trauma.

how is amblyopia treated?

In children, amblyopia is treated by prescribing the right glasses and covering the good eye with a patch, causing the brain to improve how it works with the bad eye. As children age, however, the brain becomes less plastic. As a result, amblyopia is difficult to treat in adults using this conventional method. Instead, Vision Therapy (VT) can be used to 'train' the adult brain to use the amblyopic eye. While VT has had success in improving the eyesight of adults with amblyopia, gains are limited and progress takes a lot of time.

why would you put people in complete darkness?

Studies in animals (like this and this) show that something curious happens when you deprive the eyes of light: the part of the brain that processes vision becomes open to new sensory input. This can happen in humans too. It's a quality called neural plasticity. When the visual brain becomes plastic, animals can recover significant visual acuity and possibly stereo vision. We don't know yet if this treatment will work in humans; the purpose of Project LUMA is to find out.