Diagnosis and Assessment of Strabismus

Introduction to Strabismus Diagnosis

The cover-uncover test is used to detect manifest strabismus (tropia) by covering one eye and observing whether the uncovered fellow eye makes a refixation movement, with any refixation movement indicating a positive test and confirming the presence of a tropia, as recommended by the American Academy of Ophthalmology 1

The cover-uncover test should be performed using an accommodative target at both distance and near fixation to control the patient's accommodation during testing, according to the American Academy of Ophthalmology 1, 2
The test requires sufficient visual acuity and patient cooperation to fixate on the target, with the American Academy of Pediatrics recommending alternative methods for infants or uncooperative children 2
Alignment testing should be performed before cycloplegia, as alignment may change after cycloplegic drops, as noted by the American Academy of Ophthalmology 2

A positive cover-uncover test demonstrates a refixation movement of the fellow eye when the opposite eye is covered, indicating the presence of a tropia, with the direction of this movement indicating the type of strabismus, such as esotropia (inward deviation), exotropia (outward deviation), hypertropia (upward deviation), or hypotropia (downward deviation), as described by the American Academy of Ophthalmology 1, 3, 4

Sensory tests (stereopsis) should be performed before the cover-uncover test when evaluating intermittent strabismus, as monocular occlusion during cover testing can dissociate the eyes and unmask a latent deviation or reduce stereoacuity measurements, according to the American Association for Pediatric Ophthalmology and Strabismus 5

The alternate cover test measures the total deviation, including both manifest and latent components (phorias), making it more sensitive than simple observation, and is used to quantify the amount of surgery required, as recommended by the American Academy of Ophthalmology 3

When recording cover test results, document whether refractive correction was worn during testing, the method used to measure the angle of deviation, distance and near measurements, and whether the deviation is constant or intermittent, as recommended by the American Academy of Ophthalmology 1, 2, 3, 7