In severe cases, eye muscle weaknesses can result in double vision. This is when you see two images of a single object at the same time. The images can be completely separate or overlapping, they can also be side by side or above and below each other.

Depending on the underlying cause, people can experience double vision constantly, or sometimes it’s only an occasional problem.

Double vision can sometimes be a sign of something more serious, so if you also experience eye or head pain with your double vision, call 111 or go to your nearest A&E as soon as you can.

In order for us to see a clear image, light coming into the eye must focus on an area at the back of the eye, called the retina. This is where the light messages are translated and sent on to the brain to produce the images we see.

For people who are long- or short-sighted, the light either focuses just in front of the retina, or behind it, which makes the images we see blurry. Glasses for these eye conditions are designed to bend the light coming into the eye so it focuses on the retina, producing a clear image.

If you have an eye muscle weakness, the remaining muscles work harder to prevent you seeing double vision, which can result in eye strain and headaches. In severe cases it can cause double vision.

Prism lenses work by bending the light in such a way that it compensates for an eye muscle weakness, aligning your eyes and helping to maintain comfortable vision, as well as preventing double vision.

Small amounts of prisms are usually incorporated straight into your lenses. If larger amounts of prisms are needed, then they can be trialled using a stick-on lens before adding into the lenses.