When is a squint not a squint but still a problem? What is phoria or latent squint?
Normally the two eyes are maintained in a parallel position by the controlling effect of fusion. When the two eyes look at an object, the brain tries to “fuse” the two separate images into a single image, and to do that, sends orders to the two eyes to remain in a fixed position to each other. If this fusion is removed for any reason, even by simply covering one eye, or due to weakness in vision in one eye, the eyes no longer seem straight when looked at. However, if the patient knows he is being observed or is told to make his eyes straight, he can voluntarily do so himself. Thus he has a squint, but can “voluntarily” correct it himself. This is termed phoria. It is also termed “latent” squint for as long as fusion is holding them straight the eyes will no longer squint. The importance of phoria or latent squint is that, it is a potent cause for headaches and eye aches. Recognised early, not only can frank or “apparent” squint be prevented, but it is eminently treatable in most cases
