Vertical Deviations, A–V Patterns and Skew
Key Takeaways
A and V describe the change in horizontal alignment with vertical gaze, for either esotropia or exotropia.
DVD is a dissociated upward drift and must be distinguished from oblique overaction.
Skew can mimic trochlear palsy; neurological signs and binocular torsion guide investigation.
Prism or surgery follows a measured stable pattern and the underlying mechanism.
Describe the deviation before naming a muscle
A vertical deviation can result from a paretic muscle, restriction, congenital dysinnervation, abnormal binocular development or a vestibular pathway lesion. EBOD cases may provide a head posture, a motility photograph or a pattern measured in different gaze positions. Begin with which eye is higher, whether the deviation changes with gaze or fixation, whether it is comitant, and whether there is objective or subjective torsion. Measure the horizontal deviation as well: vertical and horizontal disorders often coexist.
Use prism cover testing in primary position and diagnostically useful gaze positions, at distance and near when relevant. Check ductions and versions and compare measurements with either eye fixing. Assess head tilt and old photographs, symptoms, trauma, thyroid disease, neurological signs and previous surgery. Limited elevation in adduction is not synonymous with inferior oblique palsy; Brown syndrome and other restrictions can produce that appearance.
Patterns across upgaze and downgaze
An A pattern means relatively greater convergence in upgaze than downgaze; a V pattern means relatively greater divergence in upgaze than downgaze. The name describes the pattern of measured horizontal alignment, not whether the patient has an esotropia or exotropia. Common conventional definitions use at least 10 prism dioptres for A and 15 for V, but measurement variability and the clinical picture matter. Document the actual angle and gaze method rather than treating the threshold as the treatment indication.
Oblique dysfunction is one possible mechanism. Inferior oblique overaction often accompanies a V pattern, and superior oblique overaction an A pattern, but patterns can also reflect rectus pulley abnormalities, craniofacial anatomy or other muscle factors. A V-pattern esotropia becomes less esotropic in upgaze and more esotropic in downgaze. A V-pattern exotropia becomes more exotropic in upgaze. These are consistent descriptions of the same divergence pattern.
| Finding | Possible interpretation | What to check |
|---|---|---|
| Overelevation in adduction | Inferior oblique overaction or another cause of apparent overelevation | Torsion, horizontal pattern, dissociated deviation and restriction |
| Underdepression in adduction | Superior oblique dysfunction or restriction elsewhere | Head tilt, torsion, trauma and fellow-eye findings |
| Limitation of elevation in adduction | Brown syndrome or other restrictive process | Elevation in abduction, pain, onset and selected forced-duction assessment |
| Incomitant vertical deviation with neurological signs | Brainstem or vestibular disease, including skew | Full neurological and ocular motor examination |
Dissociated vertical deviation
Dissociated vertical deviation (DVD) commonly accompanies infantile strabismus. The covered or non-fixing eye drifts upward, often with extorsion, and returns when it resumes fixation. Its behaviour differs from a simple reciprocal hypertropia governed by ordinary Hering-law responses. Both eyes may be affected asymmetrically. DVD may be more apparent during inattention or monocular occlusion; an upward drift alone does not establish inferior oblique overaction.
Document frequency, magnitude, head posture, control and cosmetic or functional impact. Treat associated amblyopia and horizontal deviation. Selected surgical procedures include superior rectus recession or inferior oblique procedures when the motility pattern supports them. No single millimetre dose follows from the name DVD. Explain the possibility of residual or recurrent drift and distinguish the surgical goal from restoration of normal sensory fusion.
Skew and ocular tilt reaction
A skew deviation is a supranuclear vertical misalignment associated with imbalance in vestibular pathways. It may occur with brainstem or cerebellar disease and can mimic a fourth-nerve palsy. The ocular tilt reaction combines skew, ocular torsion and head tilt. Examine nystagmus, pursuit, saccades, internuclear function, gait and other neurological signs. A skew can be comitant or incomitant and is not excluded by a seemingly positive three-step test.
Torsion helps but is not infallible. In a typical trochlear palsy the hypertropic eye is excyclotorted; skew-related torsion may follow a different binocular pattern. A substantial reduction of vertical deviation when supine can support skew in an appropriate context, but absence of that response does not exclude a central lesion. Acute onset with headache, ataxia, other cranial deficits or vascular risk demands urgent assessment rather than immediate elective strabismus surgery.
Management follows the mechanism
Small stable deviations may be managed with an appropriate prism, initially a Fresnel prism if the angle is changing. Occlusion can relieve diplopia temporarily when fusion is not possible, with attention to amblyopia risk in children. Treat thyroid restriction, inflammation, neurological disease or other causes before planning definitive alignment surgery. Forced ductions and imaging are selected when restriction or orbital disease is suspected; they are not routine prerequisites for every small vertical phoria.
For a child with infantile esotropia, intermittent upward drift and no limitation of movement, DVD may be more likely than an acquired isolated nerve palsy. For an adult with abrupt vertical diplopia and ataxia, central skew is a serious consideration. In both cases, explain the observed signs before the diagnostic label and identify the finding that changes urgency. The EBO paediatric and neuro-ophthalmology syllabuses require this distinction between motor pattern, cause and management.
Sections you finish are checked off in the contents.