A pair of glasses in which one of the lenses is red and the other green. Vision therapy activities such as red/green playing cards, red/green reading charts or anaglyphs assist patients with amblyopia or strabismus to break suppression to the non-dominant eye.
The eye behind the red lens only sees a target, while the eye behind the green lens only sees a target. The patient uses the glasses and looks at a picture with red and green objects to keep both eyes working together as a team or unit.
Using the appropriate combination, conditions can be arranged so that the ‘weaker’ or lazy eye is the only eye capable of viewing the image, although both eyes are open and looking for input. The patient wears the glasses and looks at a picture with red and green objects in the scene. The red objects may be red and rich in detail, which will require more work on the part of the eye. Each eye sees a different target, so the patient gets important feedback about when he or she is suppressing the amblyopic eye.
Following feedback from the patient on which color the patient cannot see or reports this colored image has gone missing, we then know which eye is being ignored or suppressed. This suppression occurs in patients with amblyopia.
This activity uses the concept of monocular fixation in a binocular field, or MFBF. This means that both eyes work together to react to the target or scene, but only one eye at a time actually sees the given target. It works by way of keeping both eyes in the same field to “paying attention”.