About Orthoptics2023-12-01T11:51:02+00:00

About Orthoptics: common conditions

Many of the terms used in guides and articles about orthoptics will be unfamiliar to a non-Orthoptist. We have tried to provide some simple descriptions below of a number of the most common conditions as well as the types of treatment offered.

If you are experiencing visual difficulties or think you may have one of these conditions, you should see an Orthoptist. They will be able to provide you with more specialist advice, based on your individual diagnosis.

For an appointment you can ask your GP, health visitor, school nurse, optometrist or hospital consultant.

Click on the terms for further information:

Amblyopia (sometimes known as lazy eye)

Strabismus (misalignment of the eyes)

Double Vision

Blurred Vision

Refractive errors

Ptosis (drooping of the eye lid)

Nystagmus (uncontrolled constant eye movements)

Ocular head postures

Our Clinical Advisory Groups offer information on the more specialist, advanced or extended roles carried out by Orthoptists.


This condition is the most common cause for treatable reduced vision in young children. Amblyopia can also be called a “lazy eye”, meaning the vision in that eye is poorer than the other. It occurs because the vision-sensing part of the brain (visual cortex) has not been stimulated correctly and has therefore failed to develop normally, so normal visual function cannot be reached without intervention. It can occur in children who need glasses, or who have a squint (an eye that turns inwards or outwards; see strabismus). It is important to see your Orthoptist about this condition quickly as evidence shows it can be most effectively treated when your child is less than 8 years old. Prompt treatment is therefore required following diagnosis and the sooner it is diagnosed, the better the outcome after treatment.

Amblyopia can be treated in a number of different ways to stimulate visual cortex and help it to develop normally. Sometimes the only thing that is needed to do this is prescribing glasses to help your child see clearly. Other times, even after glasses have been prescribed, the visual cortex may need more stimulation, so your Orthoptist will prescribe occlusion therapy. This is where the stronger eye is covered with a patch or blurred with an eye drop, which forces the weaker eye to do more work. This stimulates the underdeveloped part of the visual cortex and improves the vision in the weaker eye.


This is the formal term for when an eye turns inwards or outwards. An eye can also turn upwards or downwards but this is not as common. It can cause reduced vision in young children, which can be treated with occlusion therapy. It can also cause double vision or blurred vision, if it develops in an older child or adulthood.

Strabismus can be corrected in a number of ways depending on the type of strabismus. Sometimes, the only thing that is needed to straighten the eyes is a pair of glasses. Sometimes, glasses alone aren’t enough, and a surgical procedure can be done to straighten the eyes further. If your strabismus is giving you double vision or blurred vision, this can be helped with a prism, which is a plastic cover that is fitted to one lens of your glasses to join any double vision. Your orthoptist specialises in strabismus and will be able to tell you what the most appropriate treatment option will be.

Double Vision

This symptom results from when one of your eyes starts to turn inwards, outwards, upwards or downwards. There can be a number of reasons why your eye starts to turn; sometimes it is due to an eye muscle weakness that you were born with that is starting to deteriorate as you get older. Other times it may be the nerve that supplies your eye muscles that becomes weak.

There are a number of ways double vision can be helped. Sometimes, glasses can help correct double vision. Exercises can also help strengthen your eye muscles and stop double vision. If exercises or glasses are not appropriate, you can be given a prism, which is a plastic cover that sticks on one lens of your glasses and will join your double vision together. Surgery can also help to stop an eye turning and stop any double vision, if all other options have been tried. Your orthoptist specialises in double vision and eye muscle/nerve issues and will be able to give you appropriate treatment plans and advice.

Blurred Vision

This can be caused by a number of different factors. Sometimes, it is as simple as needing new glasses to make your vision clearer. Other times, it can be caused by a weakness in the ability of your eyes to converge (i.e. to pull inwards when looking at something close to your nose), or diverge (i.e. to pull outwards, when you look at something far away in the distance). Your orthoptist will be able to assess your eye muscles and see if there is any weakness. They may give you eye exercises to help strengthen your eye muscles and give you better control over your eye movements. A prism can also be used to help blurred vision, which is a plastic cover that sticks on one lens of your glasses.

Refractive Errors

This is the formal term for your glasses prescription. There are two parts to your refractive error: the sphere and the cylinder. The sphere part tells you if you are long or short sighted. The cylinder part tells you if you have an astigmatism, which is when your eye is more rugby ball shaped rather than football shaped. You can be long/short sighted only or you can have a combination of long/short sightedness and astigmatism. Your optometrist will check what your refractive error is, and your orthoptist will tell you how it affects your vision and eye muscles.


This is the formal term for a droopy eyelid. One cause of ptosis can be a congenital weakness, meaning you were born with a weak lid muscle. Other causes include a weakness in the nerve that supplies your lid muscle, causing it to droop. Occasionally, a droopy lid can be associated with an abnormally small pupil. It can also be associated with jaw movement, where the lid will droop when the mouth is closed, but lift up when the mouth is opened.

It is important to see an orthoptist if you suspect a droopy lid in your child as it can cause reduced vision (see amblyopia) by blocking the light from entering the eye. A droopy lid can also cause the shape of the eyeball to change slightly, and therefore change or cause the need for glasses (see refractive error). Your orthoptist will test your child’s vision to make sure the ptosis is not affecting it. Surgery can help lift the lid and stop any vision problems. There are also non-surgical methods such as eyelid props, which are plastic frames that fit onto glasses and help hold your eyelid open.


This is the formal term given to eyes that wobble uncontrollably. This is a condition that you can be born with, and usually will not change throughout your life. If you were born with it, it is unlikely you will be aware that your eyes are wobbling, but it can cause poor vision which is difficult to treat. This is because when your eyes wobble, they cannot properly fix on a target in the same way that steady eyes do. It is important to understand that if you or your child were born with nystagmus, it is less likely that normal vision levels can be achieved but your orthoptist will strive to ensure best possible vision is achieved. If the nystagmus is severe and vision is very poor, it is possible to be registered as sight impaired to get extra support for you and/or your child. Some evidence shows nystagmus can be improved with eye muscle surgery.

If you were not born with nystagmus but your eyes start to wobble later in life, this may be due to a problem in the part of your brain that is responsible for balance. In this case you may feel your vision blur or jump around. This kind of nystagmus can usually be treated with medications.

Ocular Head Postures

Sometimes, you may feel your eyes are more comfortable when your head is turned, lifted, or tilted. This can be because of a number of reasons. If there is a weakness in one of the nerves that supplies your eye muscles, you may feel that your eyes are uncomfortable or you get double vision when you look into a specific position. So, to help keep your eyes away from that uncomfortable position, you may find moving your head, for example, turning your face to the side, will help your eyes feel more comfortable.

Head postures can also occur with wobbly eyes (see nystagmus). When you are born with wobbly eyes, sometimes, the wobbliness improves when the eyes are moved into a certain position and makes vision clearer. This will cause you to almost automatically move your head into a position where your eyes feel more comfortable. Many parents of children with nystagmus will notice their children holding their head in a certain position when reading/writing to help them see better. Your orthoptist specialises in eye muscle weaknesses and associated head postures and will be able to give you more information as to why you or your child might be adopting a head posture.