If you have been told you might benefit from prism in your glasses, or you have gone looking for prism glasses after months of unexplained headaches, it helps to understand what they actually do. Prism lenses are not a stronger prescription. They solve a different problem altogether.

What are prism glasses?

Diagram showing prism correction in glasses, with a misaligned image before and a single aligned image after
Before correction, the eye receives the image off-centre. Prism shifts the light so the image lands where it should, bringing the two eyes into alignment.

An ordinary lens corrects how sharply you see. A prism does something else: it bends light before it reaches your eye, shifting where the image lands. That small shift means your eyes no longer have to work as hard to line up on the same point.

Prism is not a separate pair of glasses. It is built into your normal lenses, so they look the same as any other pair.

Who prism glasses can help

Prism is used when the two eyes are slightly misaligned and the effort of holding them together is causing symptoms. This is known as binocular vision dysfunction. Common experiences include:

  • Headaches that regular glasses have not resolved
  • Double or overlapping vision, often coming and going
  • Eye strain and fatigue, particularly with reading or screens
  • Dizziness or unsteadiness in visually busy places
  • Neck and shoulder tension from tilting the head to compensate

Even a very small misalignment can produce significant symptoms, because the effort to correct it is constant.

When prism is not the answer

Being straightforward about this matters. Prism does not correct short-sightedness or long-sightedness, and it will not help headaches that come from another cause such as migraine, dehydration or neck problems. It is also not the right tool if your symptoms are driven by dry eye or an out-of-date prescription, both of which are far more common and simpler to fix.

Prism works when there is a measurable alignment problem driving the symptoms. That is exactly what an assessment establishes, and sometimes the answer is that something else is going on.

How prism is prescribed

Prism cannot be guessed at. We measure how your eyes align at distance and near, assess how they work together under sustained effort, and take a full history of your symptoms and daily visual demands. The amount and direction of prism is calculated from those measurements.

Our care runs across two appointments. The first is the assessment and prescription. The second is a review once you have been wearing the lenses, so we can check how you are responding and adjust if needed.

What to expect when you start wearing them

Most people adapt within a few days. Some notice relief almost immediately, others find their eyes feel different for a short period while they adjust to not working as hard. If anything feels wrong, we would rather see you sooner than have you push through it, which is part of why the second appointment exists.

Frequently Asked Questions

Do prism glasses look different to normal glasses?

No. The prism is incorporated into your regular lenses. In higher amounts a lens can look slightly thicker on one edge, but in the amounts typically used for binocular vision dysfunction it is not noticeable.

Will I need to wear them forever?

Not necessarily. Some people wear prism long term, others need it only for particular tasks such as screen work or reading. It depends on the underlying cause and how you respond.

Can prism fix double vision completely?

It often reduces or resolves double vision caused by a small misalignment. Double vision has several possible causes though, and sudden onset double vision should be assessed promptly rather than treated with lenses alone.

Do I need a referral?

No. You can book an assessment directly with us.

Book a binocular vision assessment

If headaches, eye strain or double vision have not been explained, we can check whether your eyes are aligning properly.
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