Sight problems and brain tumours

Around 28% of patients with a brain tumour report a problem with their vision (visual impairment). This could be a direct result of the tumour, or its treatments. How your vision is affected can differ depending on the location and treatment of the brain tumour.

What are the most common types of sight problems from brain tumours?

If you have a problem with your vision because of your brain tumour or as a side effect of your treatment, you can ask to be referred to an eye expert (ophthalmologist). They'll check the health of your eyes and provide tools and advice to help you carry on with your daily activities. They can also refer you to other eye specialists if needed.

Common side effects of a brain tumour or its treatment are:

Visual field loss

The visual field is the total area you can see while looking at one point. There are many different types of field loss. If the outer part of your visual field is damaged, it's called peripheral field loss.

Other types of field loss can be more obvious. You may have a quarter of your visual field affected (which is called a quadrantanopia) or half of your field affected (which is called a hemianopia). If you've lost half your field of vision on the same side in both eyes, it's called a homonymous hemianopia.

Everyday tasks, such as reading, watching television and travelling safely outdoors in new areas, can become difficult. You may often feel surprised by items or people suddenly appearing or be unaware of the field defect and unconsciously neglect the missing area of vision. This can lead to bumping into things on one side, eating half a plate of food only, or only reading half a line of print.

Coping with visual field loss

  • Typoscopes (a piece of card/paper with a window in the middle) can help with reading. You match up the typoscope with the page so it's easier to see where the beginning and end of each line is.
  • Prisms (a special type of lens that moves the image of an object) may help compensate for visual field loss. These move the image up, down, left, right or diagonally. At the beginning, this movement can cause confusion and headaches. However, over time, people adjust to the prism and can be taught how to scan the area around them with their new glasses. For short-term use, a prism can be stuck onto your glasses, or for long-term use, a prism can be included in your lenses.
  • If your central field of vision is good, glasses with small mirrors attached (hemianopic glasses) and inverted telescopes can help.

Your ophthalmologist or optometrist can refer you to a low vision clinic for an assessment for these tools.

Scanning and training methods can help you adapt to field loss. Your mobility officer or sensory mobility team can teach you how to use these methods.

Double vision (diplopia)

Double vision is when you see two images of a single object. The images may be side by side, one on top of the other, or diagonal to each other. It may happen all the time, or only in certain circumstances.

Double vision may be very obvious, or may appear as blurred vision. Young children may not be able to say that they have double vision. Instead, they may cover one eye, screw their eyes up, turn their head sideways or tilt it instead of looking straight. You may also notice one eye turning in or out which could cause double vision.

Treating double vision

You may be referred to an ophthalmologist automatically or can ask to be. They will test the cause of double vision and may refer you to an orthoptist for treatment. Treatment options can include one or a combination of:

  • glasses
  • prisms - Fresnel (temporary) prisms are most commonly used first. These are thin sheets of plastic with grooves, which are stuck onto your glasses. The power needed can vary, so you'll be advised to trial them for a few months before having the prism permanently included into your glasses
  • operations - you may need an operation to strengthen or weaken one or more of your eye muscles, so that both eyes are aligned again. These don't always last forever, so you may need more than one operation
  • eye exercises - eye exercises can be given to strengthen muscles for certain types of double vision. Please talk to your optometrist or orthoptist for more information
  • occlusion (covering of an eye) - blocking (occluding) vision in one eye can stop double vision that occurs when both eyes are open. This can be done by wearing a patch, opaque (cloudy) lenses or eye drops in the better eye.

Sensitivity to light (photophobia)

Your vision may become sensitive to light due to the treatment for your tumour. This could be short term or long term.

Light sensitivity is when your brain struggles to adjust to different levels of light. You may need to allow extra time for your eyes to adjust when moving between areas of different levels of light. This may be very uncomfortable.

Coping with photophobia

Short-term solutions for light sensitivity can be small changes, such as wearing large hats, sunglasses or tinted spectacles. These can help with glare but they may make it harder to see where you're going. In very serious cases, prosthetic contact lenses reduce the amount of light entering the eye (please discuss with an optometrist).

You may be advised to wear blue-blocking spectacle lenses. Some patients find these help with glare by blocking certain types of light. However, at the moment, the best scientific evidence does not support that these lenses can help symptoms.

The position of extra light is important to help you to see better without causing too much light sensitivity. Lighting can help you read if placed in a position where it causes the least amount of glare. A lamp below eye level that shines onto the book works best. It's also good to avoid shiny surfaces if possible, such as a polished desk.

Facial palsy and dry eyes

Some large tumours can cause facial palsy. This can lead to dry eyes or watery eyes, difficulty closing your eyes, redness, and blurring of vision.

If you cannot close your eyes, the tears in your eyes can't be spread over the eye and the surface of the eye can be exposed for long periods of time. This can cause dry, irritated eyes and increase the risk of infection.

Your bottom lid may also turn outwards (ectropion), which means the tears don't drain properly. This can lead to watery eyes and blurry vision.

Treating facial palsy and dry eyes

For mild dry eye, the most common short-term treatment is eye drops. Your optometrist can recommend which drops to use.

Your eyes can be protected by wrap-around glasses during the day and your eyelid can be taped closed at night. If your eye is very dry, you can use punctal plugs. These block the ducts in your eye to stop tears being drained. They can be removed once the palsy has had time to recover.

If the palsy doesn't resolve within six to eight weeks, there are many other longer- term treatments, including surgery, to help your lid close. For other solutions please speak to your optometrist.

Abnormal eye movements

Abnormal eye movements can come in many forms. Both your eyes may not work together to look at the same point (squint), or your eyes may wobble out of control (nystagmus). Both of these will make it harder to focus, and can cause blurry or double vision.

Coping with abnormal eye movements

Most people with acquired nystagmus have a specific direction they look in where their eye movements are the slowest. This is called a null point, and as there is no treatment for acquired nystagmus, it's normally advised that you tilt your head so that your eyes are in this position.

A member of your eye health team can help teach you about your null point. If the acquired nystagmus is extreme, surgery can be used to help place your eyes in the null position to stop you having to tilt your head.

Some patients with nystagmus find contact lenses give clearer vision as the lenses move with the eyes. Others find the contact lenses harder to put in as the eyes are wobbling and find glasses shield some of the eye movement so are more aesthetically pleasing.

Aphasia (language and speech problems)

Aphasia is where the brain cannot process words in the correct way. It affects speaking, reading and writing. You may be able to see the words correctly, but make mistakes when saying them out loud or might not be able to understand them. Sometimes, this can be mistaken for poor vision and you may be referred to a low vision clinic. They will check your eyes and see if your problems are due to your ability to recognise and process what you're looking at.

If the low vision advisor finds that your problems are due to language and literacy, they will refer you to your GP to see a Speech and Language Therapist. Find out more about communication difficulties.

If you have further questions, need to clarify any of the information on this page, or want to find out more about research and clinical trials, please contact our team:

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