Suppression

We have mentioned suppression previously so lets discuss it more thoroughly.

Our brains do not like to see double, nor do they like to see clearly out of one eye and poorly out of the other, either can be very disconcerting.   To avoid this, the brain will suppress the misaligned or blurry eye.
 

Red green glasses and flashlight

Suppression is a brain response to a ocular problem.  The brain ignores the image from the unwanted eye.  This prevents someone from from appreciating 3-d.  It also inhibits judging depth especially up close, as when threading a needle. It can cause eyestrain and hinder reading.

Suppression comes in several forms:

• Location

  • Central suppression involves only a small area of vision, right around the area of regard and the brain maintains awareness of the periphery in that eye.

  • Peripheral suppression is significantly more rare and involves both the center and the periphery, this can even make it difficult to walk across a room.

• Depth

  • Deep suppression means one eye is turned off nearly constantly and the information from that eye is entirely ignored.  Most people with this condition are unaware they have a problem but they may notice they cannot do magic eye posters and don’t notice a difference in 3-D movies.

  • Shallow suppression means one eye is turned off intermittently, and the brain may see both images.  This form is actually more troublesome because it often causes eyestrain.
     

Testing for suppression usually occurs in a doctor’s office but the technique is quite simple and it is an excellent way to describe suppression.  Red-green glasses and a flashlight with multiple lights (pictured above) are generally used.  With the glasses on, the right eye sees the red ballerina and the white ball.  Meanwhile the left eye sees the green elephant and white ball(pictured below).
 

View through the green lens

If both eyes are functioning properly then the eyes should see all three images.  If an eye is suppressed then only two images will be seen, both the white ball and the functioning eye’s color.

Treatment for suppression should be carefully considered.  While it may restore 3-D vision, it can also leave someone with permanent double vision.

“Dodge”

William Dodge Perry, OD

Falls Church VA