Pseudoexotropia is a condition in which the alignment of the eyes is straight (also known as orthotropic); however, they appear to be turned outward.[1]
See related CME at Highlights of the American Association for Pediatric Ophthalmology and Strabismus Annual Meeting.
Pseudoexotropia occurs with a wide interpupillary distance or a positive angle kappa. Angle kappa is the angle formed between 2 imaginary lines: the visual axis and the pupillary axis. To construct the visual axis, extend a straight line from the viewing object through the nodal point. A straight line going through the center of the pupil and perpendicular to the corneal plane constructs the pupillary axis. Since fovea is displaced temporally, a small angle kappa (up to 5°) manifests as a nasally displaced corneal light reflex. Children may falsely appear to have an exotropia when they look to the side.
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The incidence of pseudoexotropia is higher in children with a temporally dragged macula from retinopathy of prematurity.
No known sexual predilection exists.
The appearance of pseudoexotropia is seen at any age.
Parents bring their child to their physician, reporting that the child's eyes appear to be turned out.
Patients appear to have a large angle kappa or nasally deviated corneal light reflex. By performing the cover-uncover test, no movement can be demonstrated. In the case of a dragged macula, an ophthalmoscope examination reveals an ectopic macula displaced temporally.
A common cause of pseudoexotropia is a dragged or temporally displaced macula associated with retinopathy of prematurity.
Retinal scarring in the temporal periphery caused by Toxocara canis is another cause of a temporally displaced macula resulting in pseudoexotropia.
Cover testing does not show any refixation movement in patients with pseudoexotropia, as opposed to in patients with true exotropia.
A complete ocular examination is important for a patient who actually may have a true tropia or true exotropia.
Patients with suspected pseudoexotropia should be initially examined and then observed by an ophthalmologist because true tropia or true exotropia may later develop. For example, a large positive angle kappa may hide an esodeviation, and a negative angle kappa may hide an exodeviation.
A patient with pseudoexotropia should be observed on a regular basis to ensure no subsequent development of true strabismus.[2]
Parents of a child with pseudostrabismus should be reassured that the alignment of their child's eyes is straight (orthotropic). However, follow-up care should be continued because pseudoexotropia can hide a true strabismus.[2]