V-Pattern Strabismus

-Difference in measurement between up gaze and down gaze of at least 15 prism diopters

-V pattern exotropia - greater magnitude of deviation in up gaze than down gaze

-V pattern esotropia - greater magnitude of deviation in down gaze than up gaze

EPIDEMIOLOGY: An A or V pattern is found in 15-25% of all horizontal strabismus cases. V pattern is the most common overall

DIAGNOSIS:

-The presence of a pattern strabismus is assessed by measuring alignment in approximately 25 degrees for up gaze (chin down) and 35 degrees for down gaze (chin up) from the primary gaze position.

-The patient should be wearing the appropriate refractive correction to minimize an accommodative component.

-It is important to note any compensatory head positions, such as chin up or down.

-It is paramount to rule out a vertical pattern in every case of comitant strabismus, as our management would be defined by the same.

-Apart from the basic strabismus work-up, the additional assessment needed in the presence of patterns is to look for:

Abnormal head posture:

-Chin elevation may be seen in V-exotropia

-Chin depression may be a feature in V-esotropia.

-Measurement of deviation in primary position, 25 degrees upgaze and 35 degrees downgaze: A case of V-esotropia may be misdiagnosed as convergence excess type of esotropia.

-Similarly, V-exotropia may be confused with divergence excess type of exotropia.

-Measurement of deviation in the 3 sets of gaze will reveal the true pattern.

-Measurement of deviation in 9 gazes.

Overelevation or overdepression in adduction (measuring oblique muscle overaction).

-Ocular torsion: Objective assessment of ocular torsion can be done on fundus examination based on the relative position of macula and optic nerve head. Normally, the fovea is located 0.3 disc diameters below the horizontal line, passing through the center of the disc. In excyclotorsion, the macula lies further below this line, and in incyclotorsion, the macula lies above it.

-Orbital imaging may be considered in patients with craniofacial anomalies and in cases where the cause of the pattern cannot be identified.

SWIPE to see surgical management in V-pattern strabismus!

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