This occluder uses a lightly frosted, scratch resistant lens that degrades the acuity of the non-tested eye while not inducing suppression effects. The reading eye is thus tested with an absolute minimum of interference from the fellow eye.
The examiner is also able to see the non-tested eye through the frosting. This is important to see if the patient giving acuity results is “squinting” the fellow eye under the paddle. Likewise cover testing is made more reliable and informative because the examiner can see the movement of the covered as well as the un-covered eye.