Help and frequently asked questions

What can I do if I notice changes to and around my pupil?


The pupil plays an important role in the structure of the eye, but it can be affected by certain conditions that can cause a change in its shape or appearance. The pupil itself is an opening located right in the middle of your iris, the part that gives your eye its colour. The function of the pupil is to let in light through to the retina at the back of the eye, which is crucial for good vision. Unlike your iris, your pupil looks black because the light hitting it is all absorbed by inner eye tissues. The normal shape of a human pupil is round - in other species such as cats, it will have more of a slit shape. However, the size of your pupil will change according to the amount of light in your environment. Your iris controls the movement of the pupil, using two groups of smooth muscles to either contract or dilate the pupil to take in more or less light. When these light rays pass through into the lens and eventually the retina, this allows the the retina to convert the light into electrical impulses that are sent onto the brain for processing. If you're worried about a change in your pupil it's best to see your optometrist for more information, but here are some general tips and advice to keep in mind if you notice any one of the following changes. Grey ring around the pupilIf you notice the appearance of a grey ring around your pupil, you don't need to worry as in most cases this won't affect your vision. The ring is called an arcus and tends to be a normal occurrence for people who are over the age of 40. It consists of cholesterol deposits that build up in the outer edge of the cornea, the clear surface covering the front of your eye. It will usually appear to circle around the iris rather than the pupil. There is no treatment required, however it may be a good indication to visit your doctor for a cholesterol check.

Problems with dilation of the pupils

If you notice that one pupil is dilated and the other isn't or they have varying degrees of dilation between them, it can be a sign of aniscocoria. This condition is characterised by having pupils of different sizes. Physiologic aniscocoria poses no problems to vision, but other types can be an indicator of a more serious eye condition.Aniscocoria can be caused by a variety of factors from viral infection to surgical damage, and it's important to see your optometrist immediately if you notice your pupil sizes are different in each eye.

Pulsating pupils

Sometimes you might notice your pupils are 'pulsating' or changing shape even when there haven't been any changes in the light surrounding you. It's important to note that pupils frequently change size, especially in younger people, and they can make active adjustments on their own quite regularly. As long as your pupils continue to react to light normally then there should be no lasting problems. However, if you are experiencing other symptoms such as pain, dizziness or nausea you should get an eye test from a professional optometrist to check whether there are any underlying issues. Other pupil concernsIf you notice yellow lines appearing through your iris and connecting to the pupil, this is generally no cause for concern. It could be a sign of Persistent Pupillary Membrane, a condition where your eye still has some remnants of a membrane that is present at birth. This usually disappears during the first few weeks of life, but in some people it can linger. It is not associated with any vision problems.Sometimes you might think one pupil looks higher than the other. In most cases this will be a result of one eyelid being slightly lower than the other, giving off the asymmetrical effect. This is normal in many people.  However if you have noticed this difference recently, it is important to visit your optometrist.