A phoria is a type of eye misalignment that only becomes apparent when the normal binocular vision is disrupted. In essence, it's a latent tendency for the eyes to drift out of alignment when they aren't actively working together to focus on a single point. This misalignment is not visible when both eyes are working together normally.
Understanding Phoria
Here's a breakdown of what makes a phoria:
- Latent Misalignment: Phorias are not a constant misalignment. They only emerge when binocular vision is broken. This can happen when one eye is covered or when the brain is unable to combine the two images received by each eye into one.
- Binocular Vision: Normally, our eyes work in tandem, and our brain combines the slightly different images from each eye into a single, three-dimensional image. This is binocular vision.
- Disruption of Binocular Vision: When binocular vision is interrupted, such as when one eye is covered, the eyes might drift. It is at this point that a phoria is revealed.
- Temporary Misalignment: This misalignment during a phoria is not permanent. When binocular vision is restored, the eyes return to their aligned position.
- Common Condition: Phorias are actually very common, and most people have some degree of phoria. Usually, the brain can compensate for it and maintain normal binocular vision.
Types of Phorias
Phorias are named based on the direction the eyes drift when binocular vision is interrupted. Some common types include:
| Type | Description |
|---|---|
| Esophoria | The eyes tend to drift inward (toward the nose). |
| Exophoria | The eyes tend to drift outward (away from the nose). |
| Hyperphoria | One eye tends to drift upward. |
| Hypophoria | One eye tends to drift downward. |
| Cyclophoria | The eye tends to rotate (This one is far less common than the others) |
Symptoms and Detection
Most phorias do not cause noticeable symptoms, because the visual system can usually compensate effectively. However, some individuals may experience:
- Eye strain or fatigue
- Headaches
- Blurred vision
- Double vision (less common)
- Difficulty concentrating on reading or close-up work
Phorias are typically diagnosed during a comprehensive eye exam where a variety of tests are performed, which allow optometrists and ophthalmologists to measure eye alignment. The covering and uncovering one of the eyes is a common method for detecting and measuring phoria.
Management
In most cases, phorias do not need treatment. However, if the phoria is causing symptoms, a doctor might recommend:
- Vision therapy: Exercises that help strengthen eye muscles and improve eye coordination
- Corrective lenses: Eyeglasses or contact lenses can sometimes help reduce the strain of a phoria
- Prism lenses: Specific lenses with prism can be prescribed to help shift the image and alleviate eye strain
Conclusion
A phoria is a latent eye misalignment that only becomes visible when binocular vision is disrupted and the two eyes are no longer looking at the same object.
