Vision Screening Online Training Program

Module 7: Stereo Acuity Test - Random Dot E
(C&TC: Usually performed by a nurse or medical assistant)

Testing for stereo acuity is checking the child’s ability to discern depth or distance of an object. To have depth perception, both eyes must work together. When both eyes are properly functioning, the brain fuses the two images gained from each eye to form one image. If one eye is not functioning properly, as in the case of strabismus or amblyopia, the child’s brain will be unable or will have a difficult time fusing images, affecting their ability to see depth properly. In these cases, the child will not be able to see the image portrayed on the stereo acuity test.

Stereopsis measurement should be performed before the eyes are dissociated by tests such as the cover test.

Ages: Age 3 years through 8 years (C&TC) or 3rd grade (Early Childhood and school screenings).
Purpose: To check for problems with stereo acuity or depth perception which tend to be an occurrence for children with strabismus.
Description: By noting if the child is able to see the raised “E” while wearing special glasses, the observer is able to check for stereo acuity problems.
Equipment:

Random Dot E stereo card, blank stereo card, model E card, and polarized glasses.

Random Dot E cards and glasses
Random Dot E. Stereo Optimal Company, Inc. Chicago, IL

Facilities: A well-lit, glare free location.
Procedure:
  1. Place the polarized glasses on the child. Do not remove prescription glasses if the child wears them
    • (Hint: If the child hesitates, tell him or her that you are putting on glasses that look like sunglasses or that they are magic glasses so they can see magic pictures.)
    • If the polarized glasses are too large for the child, put a short piece of masking tape on the top of the glasses and use the other end of the tape to hold the glasses on the child’s forehead.
    • When showing the child the test targets, be sure he/she keeps his/her head straight up, as tilting to one side or allowing the glasses to tilt on his nose, will interfere with the test.
  2. At 20 inches away from the child, hold the sample model E card with the long sides on the top and bottom. Ask the child what the figure is. If the child cannot name it or has difficulty naming it, point at the E figure on the card and say “that’s an E.

    Screener at 20 inches away from child

  3. With the polarized glasses still on, practice using the sample card and blank together by mixing up the cards behind your back and presenting the cards to the child. Have the child point to the card with the ‘E” on it. Do this 4-5 times.
  4. Substitute the model E care with the stereo E card. Tell the child that, “sometimes, while wearing the magic glasses, he may see a “picture” appear on the card.” Mix the blank card and stereo E card behind your back and present the cards to the child. Have the child identify the card they see a picture in. Do this 5 times.
    • (Note: Slightly rotate (don’t tilt) cards up and down to pick up light to give optimal viewing of the stereo image.)
  5. Move back to 40 inches from the child and repeat step 4.

Screener at 40 inches away from child.

 

Pass: Child is able to point to the correct stereo E card at least 4 times at 20 inches and 40 inches.
Re-screen/
Refer:
The child cannot distinguish the E figure in the RDE card at all, or can only see it when the card is approximately 20 inches or closer.


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