Heterophoria: Strabismus in certain situations
Heterophoria is colloquially also called latent or hidden strabismus because it can usually be compensated well. This means that those affected do not have any complaints.
The background of the phenomenon is as follows: The individual traction of the eye muscles varies from eye to eye. If you focus on an object with both eyes, however, this difference is compensated for by the brain’s sensory processing – a process called fusion, which prevents double images. For many people, however, this no longer works in certain situations: if they are very tired or have drunk alcohol, for example, the two eyes no longer work together properly – heterophoria becomes noticeable.
This latent strabismus is not at all rare: Estimates suggest that 70 percent of all people are affected.
Diagnosis by means of a cover test
Once an eye is covered, it corrects its focus to its favorite position under the cover. This can be determined by the ophthalmologist. The cover test is also used to measure the squint angle. To do this, various instruments are used to determine the angle of correction that the eye must make when it rejoins the second eye from its favorite position.
Heterophoria: symptoms
Heterophoria must be distinguished from the rest of strabismus. It is a norm variant of latent strabismus, which is even more common than two eyes with completely matching visual axes. As the brain corrects the visual axes, there is a spatial visual impression and complete processing of the image information.
Heterophoria: Therapy
Therapy of heterophoria is necessary only in rare cases – latent strabismus has no disease value.
However, certain movement exercises can be done to restore the muscular balance between the eye muscles. Other patients become symptom-free when they are fitted with glasses that precisely match their eye values. If someone still has complaints despite wearing glasses, special prism glasses can be used. They correct the angle defect.
In very rare cases, surgical intervention is necessary for heterophoria.