Diagnosis of Unilateral and Alternating Strabismus Unilateral Cover Test

A unilateral cover test can distinguish between manifest unilateral strabismus and alternating strabismus. The patient is requested to fixate on a point. The examiner than covers one eye and observes the uncovered eye (Fig. 17.8a -c).

❖ In unilateral strabismus, the same eye always deviates. When the deviating eye is covered, the uncovered eye (the leading, nondeviating eye) remains focused on the point of fixation. When the nondeviating eye is covered, the uncovered deviating eye has to take the lead. To do so, it will first make a visible adjustment. In esotropia, this adjustment is from medial to lateral; in exotropia, it is from lateral to medial.

❖ In bilateral alternating strabismus, both eyes will alternately fixate and deviate.

— Diagnosis of strabismus in children with the Teller acuity card. -

— Diagnosis of strabismus in children with the Teller acuity card. -

Teller Acuity Card
Fig. 17.7 The Teller acuity card is located in a viewing case behind which the examiner sits. This permits the examiner to see upon which half of the card the infant fixates. Infants who prefer the striped side have good fixation.

— Response of the deviating eye to a unilateral cover test.

— Response of the deviating eye to a unilateral cover test.

Cover Test For Eyes

Fig. 17.8 a Unilateral esotropia of the right eye. b Unilateral cover test: When the leading left eye is covered, the deviating right eye adjusts with a movement from medial to lateral and then takes the lead. The covered left eye deviates. c When the leading left eye is uncovered again, the right eye reverts to its deviation. The leading left eye is realigned with the fixation point.

Fig. 17.8 a Unilateral esotropia of the right eye. b Unilateral cover test: When the leading left eye is covered, the deviating right eye adjusts with a movement from medial to lateral and then takes the lead. The covered left eye deviates. c When the leading left eye is uncovered again, the right eye reverts to its deviation. The leading left eye is realigned with the fixation point.

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Responses

  • petra
    How to perform unilateral and alternating cover test?
    1 year ago

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