Skew deviation is a specific type of strabismus, which is a broader term for eye misalignment.
Strabismus is the general medical term used to describe eyes that do not properly align with each other when a person is looking at an object. This misalignment can involve the eyes turning inward, outward, upward, or downward. It can be constant or intermittent.
According to the provided reference, "Skew deviation is an unusual ocular deviation (strabismus)". This means skew deviation falls under the umbrella of strabismus but has distinct characteristics.
Key Differences Explained
The primary difference lies in the nature of the misalignment and its underlying cause.
What is Strabismus?
- Definition: A general term for any condition where the eyes are misaligned and do not point in the same direction.
- Misalignment Types: Can be horizontal (esotropia - inward turn, exotropia - outward turn) or vertical (hypertropia - upward turn, hypotropia - downward turn).
- Causes: Can vary widely, including genetic factors, refractive errors, nerve damage, muscle disorders, or other medical conditions.
- Occurrence: Can be present from birth, develop in childhood, or appear later in life due to illness or injury.
What is Skew Deviation?
- Definition: A specific, unusual type of ocular deviation (strabismus).
- Misalignment Type: Characterized specifically as a vertical misalignment (hypertropia), where "the eyes move upward... in opposite directions." This typically means one eye is higher than the other, and this vertical difference can change depending on gaze direction.
- Cause: Unlike many other forms of strabismus, skew deviation is caused by "abnormal prenuclear vestibular input to the ocular motor nuclei." This often results from neurological issues, "most commonly due to brainstem or cerebellar stroke."
- Occurrence: Usually associated with acquired neurological conditions affecting the brainstem or cerebellum.
Strabismus vs. Skew Deviation: A Comparison
Here is a simple comparison highlighting the distinctions:
| Feature | Strabismus | Skew Deviation |
|---|---|---|
| Classification | General term for eye misalignment | Specific type of strabismus |
| Misalignment | Horizontal, Vertical, or combined | Specifically vertical (hypertropia) |
| Eye Movement | Can be inward, outward, up, or down | Eyes typically move upward in opposite directions |
| Primary Cause | Various (muscles, nerves, genetics, refractive errors, etc.) | Abnormal vestibular input, often due to brainstem or cerebellar stroke |
| Related To | Can be congenital or acquired | Typically acquired due to neurological conditions |
In essence, all skew deviations are a form of strabismus, but not all strabismus cases are skew deviation. Skew deviation is a particular manifestation of strabismus with a specific vertical pattern and neurological origin.
