Heterophoria (Latent Squint)
Heterophoria is a tendency of the eyes to drift out of parallel alignment which stays invisible in everyday life, because the brain holds the eyes in the correct position through the mechanism of fusion — the merging of two images into one.
The difference between a manifest and a latent squint is not the size of the deviation, but whether the system keeps control of it. In heterophoria it does. The eyes stay correctly aligned for as long as they work together — only breaking that cooperation reveals the tendency to drift.
That is why heterophoria is found by examination, not by observation. During the cover test the examiner briefly covers one eye, interrupting the merging of the images. The covered eye then settles into its resting position, and on being uncovered it moves back into place — and that return movement is what the examiner is looking for.
The mere presence of heterophoria is common and in most people causes no complaints at all. What matters is the situation in which the system stops coping with it — this is referred to as decompensation.
National guidelines indicate that orthoptic exercises have a proven use precisely in latent squints, when these are the cause of asthenopic symptoms, and in convergence insufficiency. Beyond these indications, there is a lack of scientific evidence for their effectiveness.
Heterophoria is identified by an examination with a specialist — ocu•vio does not assess eye alignment and does not replace such an examination. If a child is under specialist care, the choice of any home activities is made by the supervising person.
Frequently Asked Questions
How does a latent squint differ from a manifest one?
Not in the size of the deviation, but in whether the system keeps control of it. In a latent squint the eyes stay correctly aligned as long as they work together — the deviation appears only once that cooperation is interrupted.
Why can a latent squint not be seen at home?
Because the mechanism that merges the images from both eyes keeps holding the eyes in the correct position. The deviation is revealed only by the cover test, in which the examiner briefly interrupts that cooperation.
Does a latent squint always require management?
No. In most people it is present and causes no complaints. What matters is the moment when the system stops coping with it and fatigue symptoms appear.
When do orthoptic exercises have a proven use here?
National guidelines list latent squints that cause asthenopic symptoms, and convergence insufficiency. Beyond these indications, there is a lack of scientific evidence for effectiveness.
Related concepts
Source: Polish Ophthalmological Society, Section of Paediatric Ophthalmology and Strabismus, Wytyczne postępowania w zezie [Guidelines on the management of strabismus], 2021.
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