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Three levels of binocular vision

The images from our two eyes is melted together in our visual cortex in the brain. This is a really complicated precess that is hard to understand. Binocular vision is generally considered to be able to look at the same object at the same time with both eyes, thus giving us perception of depth. However, binocular vision can be devided into three levels of functionality.

Seeing with both eyes simultaneously

The first level of binocular vision is the ability to process images from both eyes at the same time.

Fusion – two images is merged into one

Fusion means that the brain is able to interpret the two different images from right and left eye correctly and is able to give a single image as output. This happens if we are able to direct the two eyes in the same direction and focus on the same object. With the information from two eyes, most of us have a slightly higher visual acuity than with only one eye.

Stereopsis – distance, depth and direction 

Stereopsis is our ability to see three dimentional. This depth of vision comes from the small differencies in the images from the two eyes. The brain uses these clues to help us assess distance to objects. With only one eye, it is possible to learn how to use other clues. People who are born with only one functioning eye do this fairly good but if loosing one eye when you are ad adult, it can be more difficult to learn this. Try yourself to cover one eye and pour some water in a cup, it's not so easy without the stereopsis.

What are the symptoms of poor binocular vision? 

We all react different but if you experience some of the symptoms described below, it's a good idea to see an eye care professional to examine the cause.

  • General eye strain (asthenopia), blurred vision, photophobia 
  • Abnormal head posture
  • Headache, pain in or behind the eyes
  • Diplopia, poor determination of distance
  • Dizziness, nausea
  • Stumbling, general clumsiness
  • Squinting
  • Poor stamina when reading, trouble keeping focus