[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Ophthalmology](https://durgical.com/en/ophthalmology/) › [The eye exam](https://durgical.com/en/ophthalmology/areas/exam/) › Eye movements and the cover test # Eye movements and the cover test - Examination The corneal light reflex, the cover tests and the nine positions of gaze show whether the eyes are aligned and which muscle or nerve is weak. Updated Nov 5, 2026 **See it in 3D:** [Medial rectus](https://durgical.com/en/anatomy/medial-rectus-muscle/) · [Lateral rectus](https://durgical.com/en/anatomy/lateral-rectus-muscle/) · [Superior rectus](https://durgical.com/en/anatomy/superior-rectus-muscle/) · [Inferior rectus](https://durgical.com/en/anatomy/inferior-rectus-muscle/) · [Superior oblique](https://durgical.com/en/anatomy/superior-oblique-muscle/) · [Inferior oblique](https://durgical.com/en/anatomy/inferior-oblique-muscle/) ## Key points - Cover-uncover finds tropias; alternate cover finds phorias. - Symmetrical light reflex with wide nasal bridge = pseudostrabismus. - Constant strabismus in a child = refer (amblyopia, tumour). - Nine positions of gaze localise the weak muscle. ## What it is Eye alignment is checked first with the corneal light reflex (Hirschberg test) and then with cover tests, which reveal a manifest deviation (tropia) or a latent one held in check by fusion (phoria). Eye movements are tested in the nine positions of gaze, first with both eyes (versions) and then each eye alone (ductions). Together they diagnose strabismus in children and localise cranial nerve palsies and restrictive problems in adults. ## Normal values and scales - In the Hirschberg test each millimetre of displacement of the reflex is roughly 7 degrees, or 15 prism dioptres, of deviation. - Esotropia: eye turned in; exotropia: turned out; hypertropia: turned up. - Each extraocular muscle acts most in one diagnostic position of gaze. - In a third nerve palsy the eye rests down and out; in a sixth nerve palsy it cannot abduct. - The head tilt test helps identify a fourth nerve palsy. ## How it is done - Shine a penlight from about a third of a metre and compare where the reflection falls on each cornea. - Cover-uncover test: cover one eye while the patient fixes a target; if the uncovered eye moves to take up fixation, it was deviated (tropia). - Repeat for the other eye. - Alternate cover test: move the cover from eye to eye without letting both see; movement that appears only now is a latent deviation (phoria). - Test near and distance targets: some deviations change with focusing. - Ask the patient to follow a target into the nine positions of gaze, noting limitation, overaction, nystagmus and diplopia. - If movement is limited with both eyes, test each eye alone. ## How to interpret it - A wide nasal bridge and epicanthal folds can mimic esotropia in infants (pseudostrabismus): the light reflex is symmetrical. - Intermittent misalignment is common in the first months of life; a constant deviation at any age, or any deviation after about 4 months, is abnormal. - Restriction (thyroid eye disease, orbital fracture) limits movement in the direction opposite the tight or trapped muscle. ## Next step / Initial management - Any constant strabismus in a child, or intermittent strabismus after about 4 months: paediatric ophthalmology, with a red reflex and fundus exam. - New adult strabismus with diplopia: follow the diplopia pathway (pupil, other nerves, imaging when indicated). - Restricted upgaze after facial trauma: CT of the orbits and maxillofacial or ophthalmology referral; urgent in children. - Latent deviations (phorias) without symptoms need no treatment. ## Test yourself Think of the answer, then tap the question to see it. ## On the cover-uncover test the uncovered eye moves outward to fixate. What is the deviation? An esotropia: the eye was turned in and moves out to take up fixation. ## What does the alternate cover test reveal that the cover-uncover test does not? A latent deviation (phoria), held straight by fusion when both eyes are open. ## How is pseudostrabismus told apart from true esotropia in an infant? The corneal light reflexes are symmetrical and the cover test shows no movement. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/ophthalmology/eye-movements-and-the-cover-test/) ## Elsewhere in DurgiPedia - [Eye exam: visual acuity, visual fields and eye movements](https://durgical.com/en/clinical-exam/eye-exam-visual-acuity-visual-fields-and-eye-movements/) ## Connections ## See it in 3D 6 The structures of Durgical's 3D anatomy where it is found. - [Medial rectus](https://durgical.com/en/anatomy/medial-rectus-muscle/) - [Lateral rectus](https://durgical.com/en/anatomy/lateral-rectus-muscle/) - [Superior rectus](https://durgical.com/en/anatomy/superior-rectus-muscle/) - [Inferior rectus](https://durgical.com/en/anatomy/inferior-rectus-muscle/) - [Superior oblique](https://durgical.com/en/anatomy/superior-oblique-muscle/) - [Inferior oblique](https://durgical.com/en/anatomy/inferior-oblique-muscle/) ## Related 4 - [Double vision: monocular or binocular](https://durgical.com/en/ophthalmology/double-vision-monocular-or-binocular/) - [Extraocular muscles and the cardinal positions of gaze](https://durgical.com/en/ophthalmology/extraocular-muscles-and-the-cardinal-positions-of-gaze/) - [Strabismus in children: esotropia, exotropia, pseudostrabismus](https://durgical.com/en/ophthalmology/strabismus-in-children-esotropia-exotropia-pseudostrabismus/) - [Amblyopia: the critical period, patching and atropine](https://durgical.com/en/ophthalmology/amblyopia-the-critical-period-patching-and-atropine/) ## Related conditions 4 - [Strabismus and amblyopia](https://durgical.com/en/conditions/strabismus-and-amblyopia/) - [Oculomotor (third) nerve palsy](https://durgical.com/en/conditions/oculomotor-nerve-palsy/) - [Thyroid eye disease (Graves orbitopathy)](https://durgical.com/en/conditions/thyroid-eye-disease/) - [Orbital floor (blowout) fracture](https://durgical.com/en/conditions/orbital-floor-fracture/) [← All of ophthalmology](https://durgical.com/en/ophthalmology/) Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once. Sources: [Strabismus](https://www.ncbi.nlm.nih.gov/books/NBK560782/) (StatPearls Publishing (NCBI Bookshelf), 2026); [Esotropia](https://www.ncbi.nlm.nih.gov/books/NBK578207/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Diplopia](https://www.ncbi.nlm.nih.gov/books/NBK441905/) (StatPearls Publishing (NCBI Bookshelf), 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/ophthalmology/eye-movements-and-the-cover-test/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ophthalmology/eye-movements-and-the-cover-test/