Exophoria is an eye condition affecting binocular vision and eye alignment. It's characterized by a tendency for one or both eyes to drift outward, away from the nose, especially when the eyes are at rest or not focusing on a near object. While a small degree of misalignment is considered normal, significant exophoria can cause problems.
Understanding Exophoria
Exophoria is a type of latent strabismus, meaning the eye misalignment isn't always visible. Unlike exotropia (where the eye turns outward constantly), exophoria only becomes apparent when the fusion reflex (the brain's ability to combine images from both eyes into a single image) is interrupted. This often happens when covering one eye. When this happens, the uncovered eye may drift outward.
Several sources describe exophoria as a result of poor eye coordination. The eyes don't work together effectively, causing one eye to drift away from the other. This outward drift can lead to various symptoms, including:
- Eye strain: Difficulty focusing and maintaining clear vision.
- Headaches: Frequent headaches, especially after prolonged near-work activities.
- Double vision (diplopia): Seeing two images instead of one. This is less common in exophoria than in exotropia.
- Blurry vision: Difficulty focusing at different distances.
Causes of Exophoria
The underlying causes of exophoria are not fully understood, but several factors may contribute:
- Muscle imbalances: Weakness or imbalance in the eye muscles responsible for inward movement.
- Neurological issues: Problems with the brain's control over eye movements.
- Genetic factors: A family history of eye alignment problems may increase the risk.
Diagnosis and Treatment
Diagnosis typically involves a comprehensive eye examination by an ophthalmologist or optometrist. Tests may include cover tests to assess eye alignment and assess the amount of exophoria. Treatment options may include:
- Prism glasses: Prisms in the eyeglasses help redirect light to align the images on the retinas, reducing eye strain and double vision.
- Vision therapy: Exercises to strengthen eye muscles and improve coordination.
- Orthoptics: A specialized form of vision therapy that uses specific techniques to improve binocular vision.
- Surgery: In severe cases, surgery may be necessary to correct muscle imbalances.
Exophoria vs. Exotropia
It's crucial to distinguish exophoria from exotropia. While both involve outward eye turning, exophoria is latent (hidden unless the fusion reflex is disrupted), while exotropia is manifest (always visible).
