V pattern strabismus is a specific form of eye misalignment, or strabismus, where the deviation of the eyes changes depending on whether one is looking up or down. This condition involves a difference in horizontal eye alignment as the gaze shifts vertically.
Understanding V Pattern Strabismus
In V-pattern esotropia, the eyes show a greater inward turn (convergence) when looking down compared to looking up. Conversely, in V-pattern exotropia, the eyes exhibit a greater outward turn (divergence) when looking up than when looking down. A significant V pattern is diagnosed when the difference in horizontal deviation between upgaze and downgaze is 15 prism diopters or more.
V pattern strabismus is often contrasted with A pattern strabismus, where the horizontal deviation changes differently with vertical eye movements. For example, A-pattern esotropia shows more convergence in upgaze, while A-pattern exotropia shows more divergence in downgaze. These patterns occur in about 15-25% of horizontal strabismus cases.
Recognizing the Signs
Individuals with V pattern strabismus show a noticeable misalignment of the eyes. The eyes appear to turn inward or outward more significantly depending on whether the person is looking up or down. For instance, someone with V-pattern esotropia might appear more cross-eyed when reading or looking at their feet.
Compensatory head postures are adopted to improve vision and eye alignment. A person with V-pattern esotropia might tilt their chin up to reduce inward deviation, while someone with V-pattern exotropia might depress their chin to lessen the outward turn. Symptoms can include double vision (diplopia), eye strain, or difficulty with tasks requiring precise near or far vision.
Causes and Diagnosis
V pattern strabismus can be attributed to several factors involving the extraocular muscles, often involving the complex interplay of the extraocular muscles. These include dysfunction of the oblique muscles, such as overaction of the inferior oblique muscles or underaction of the superior oblique muscles, which can lead to a V pattern. Anomalies in the insertions of the horizontal rectus muscles or the position of the orbital pulleys can also contribute. Certain craniofacial anomalies or conditions like hydrocephalus may also be associated.
Diagnosis involves an eye examination by an ophthalmologist or optometrist. The professional measures the horizontal deviation of the eyes in various gaze positions, including straight ahead, upgaze, and downgaze. These measurements help determine the magnitude of the deviation. Observing any compensatory head postures, like a chin-up or chin-down position, also aids in diagnosis.
Treatment Approaches
Managing V pattern strabismus involves various approaches aimed at improving eye alignment, restoring binocular vision, and alleviating symptoms. Non-surgical options include optical correction with eyeglasses, especially if a refractive error contributes to the condition. Prism lenses can also be incorporated into glasses to bend light, helping to align images and reduce double vision. Vision therapy, a program of eye exercises, aims to improve eye coordination and control.
When non-surgical methods are insufficient, surgical intervention is considered. The type of surgery depends on the specific cause and presentation of the V pattern. If overaction of the inferior oblique muscles is a factor, weakening procedures, such as inferior oblique myectomy or recession, may be performed.
Another surgical strategy involves vertically transposing the horizontal rectus muscles. For V patterns, the medial rectus muscles are shifted downward, and the lateral rectus muscles are shifted upward. This repositioning alters the muscle’s pulling direction to help reduce the V pattern. The goal of these treatments is to reduce the difference in deviation between upgaze and downgaze, aiming for a more aligned and comfortable visual experience.