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Advice regarding glasses for children - Parent information

Patient information A-Z

What is a “glasses test”?

A glasses test, known as refraction, is usually performed as part of a routine eye examination. Firstly, your child’s pupils will need to be enlarged (dilated) using eye drops. This allows the ophthalmologist/optometrist to shine a bright light into your child’s eyes, enabling them to get a good view of the back of the eyes. The ophthalmologist/optometrist will then use different types of lenses to determine what strength of glasses are required to achieve the best possible vision.

My child needs glasses, should they wear glasses all day?

Yes. Children aged eight years or younger should wear glasses full-time unless they have been advised otherwise by their orthoptist, optometrist or ophthalmologist. Full time wear of glasses means wearing the glasses all day but they may be removed at bath time and bedtime only. There is a critical period for visual development and if glasses are not worn as prescribed, then a permanent reduction in vision may occur.

Why does my child’s vision not improve with glasses?

This is a regular occurrence when children are given their first pair of glasses, especially if they are long sighted. Without glasses, your child has to make a lot of extra effort to focus and see clearly. With the glasses on, your child needs to get used to relaxing their eyes to allow the glasses to do the work for them.

The glasses lens puts a clear image on the retina (back of the eye) but a child’s brain is still developing vision and needs to learn to see clearly. It can take up to 18 weeks of full time glasses wear for your child to adapt to the glasses and for the vision to improve so it is very important to persevere and encourage your child to wear their glasses all the time. You may find that your child responds well to reward charts or is motivated by other reward systems.

Will my child always need glasses?

This depends on their prescription and if they have an associated squint. Generally most children are advised to wear their glasses whilst their vision is continuing to develop up until the age of 8 years old. After this time, if your child has a small amount of long sight, it may be possible for your child to manage without glasses.

However, short sight tends to increase with age which means your child will usually continue to wear glasses. Astigmatism distorts vision for near and distance, and can only be corrected with glasses. Glasses may also continue to be needed where children have squints that are improved by wearing glasses or where surgery is not an option, but in these cases, your child may be able to wear contact lenses in the future which will have the same effect as wearing glasses to correct the squint. The decision on discontinuing glasses wear should be discussed with the clinician.

Refractive errors – explaining the need for glasses

Normal vision

Rays of light enter the eye and are focused onto the back of the eye (retina) giving a clear focused image (diagram A).

Diagram of 'normal vision': a circle symbolising the eye, a red mark on the right side labelled 'retina' and a larger yellow mark on the left side labelled 'light', lines show light travelling up to the retina
Diagram A

Hypermetropia – long sighted

The eyeball is too small / short resulting in light entering the eye and focusing behind the retina instead of directly on it (diagram B). Vision can appear blurred at all distances unless the eyes make an extra effort to focus - this may result in one of their eyes turning inwards.

Diagram of eye showing Hypermetropia - Long-sighted: A circle symbolising an eye with a yellow mark on the left side (light) and a red mark on the right side (retina), lines show the light travelling behind the retina
Diagram B

Myopia – short sighted

The eyeball is larger resulting in light entering the eye and focusing in front of the retina instead of directly on it (diagram C). Vision can appear blurred at all distances, but more so in the distance.

Diagram of eye showing Myopia – short sighted: A circle symbolising an eye with a yellow mark on the left side (light) and a red mark on the right side (retina), lines show the light travelling in front of the retina
Diagram C


This can occur on its’ own or in addition to being long or short sighted. The cornea (the front surface of the eye) is described as a rugby ball shape, rather than a regular round football shape so there are multiple focal points (diagram D). In this instance, vision is blurred/distorted for objects both near and in the distance.

Diagram showing astigmatism: A circle symbolising an eye with a yellow mark on the left side (light) and a red mark on the right side (retina), lines show multiple focal points travelling up to the retina
Diagram D


This occurs when there is a difference in the amount of long/short sight or astigmatism in each eye, resulting in blurred vision.

My child has been given a HESP form. What is it?

All children under 16 years of age in need of glasses are issued with a glasses prescription voucher (HESP form). This entitles you to help towards the cost of the glasses. The optician who dispenses the glasses will be able to tell you the exact amount you are entitled to. If the glasses you choose cost more than the value of the voucher, then you will need to pay the difference.

What should I do with the voucher?

The voucher may be taken to any registered optometrist or dispensing optician, who will make up the glasses for you. If your child needs a special type of glasses frame or has a complex prescription, you may be advised by the ophthalmologist to take the voucher to the hospital dispensing optician, who is experienced in fitting children’s glasses. Please ask a member of staff for the days and times that the dispensing optician is available (or ring the number in the contacts section of this leaflet). It is important that you take your child with you, both when you go to choose and collect the glasses, so that the glasses can be measured and fitted accurately.

What does the information on the HESP form mean?

Your child’s glasses prescription will be written on a HES(P) form which includes a table similar to the example displayed below. The prescription is divided into two halves; right eye and left eye. The top half relates to the prescription needed for distant vision and the bottom half is for near vision.

An example of a glasses prescription found on an HESP form: A table with 'left' and 'right' columns for Sph, Cyl, Axis, Prism and Base
Example of a prescription (table is for illustration purposes only).
  • The “Sph” (short for sphere) refers to the amount of long or short sight present in the prescription. The higher the number, the stronger power of the lens. A (+) indicates a long sighted lens, whereas (-) indicates a short sighted lens.
  • The “Cyl” (short for cylinder) is the extent of astigmatism in the prescription.
  • The “Axis” describes the direction and angle of the “Cyl” astigmatism. The Cyl and Axis box may be empty if there is no astigmatism correction required.
  • The “Near” prescription refers to the added magnifying power applied to the bottom part of your bifocals or varifocals to help correct any difficulty with focussing, if applicable.
  • The prism and base boxes will indicate if your child requires any prism lenses to help correct any muscle imbalances. It is extremely rare for a child to be prescribed prisms.

What happens if the glasses get broken or lost?

Should the glasses get lost, damaged or the lenses get scratched, you should take them to an optician of your choice. It does not necessarily need to be returned to the practice who supplied the original pair. They may be able to repair, re-glaze or replace the glasses free of charge. The optician does not need another voucher from the hospital to do this as they are able to reclaim their costs by filling in a NHS repair and replacement form (GOS4 optical voucher).

Extra spare pairs of glasses

Each child is entitled to one voucher per prescription. Vouchers for spare pairs of glasses are normally only supplied under exceptional circumstances, for example, a complex prescription, or glasses needing a tint such as prescription sunglasses required due to an additional underlying medical condition. In most circumstances the cost of extra or spare pairs of glasses, prescription sunglasses or swimming goggles etc., is covered by the parents/carer.

Choosing the correct fit of glasses

Children’s glasses often get broken or damaged. Be sure not to choose a frame that is too narrow as this will allow your child to look over the top of their glasses. Also ensure that the arms of the glasses loop behind the ears. This will assist in ‘anchoring’ the glasses in place and prevent them from sliding down your child’s nose.

It is important that the frames are always well maintained, that they fit comfortably and are positioned correctly so that your child is always looking through the optical centre of the lenses.

Glasses for infants have many special adaptations available such as curly ear pieces, special nose pads and head bands to help to achieve a comfortable, snug fit. Ask your optometrist or dispensing optician about these.

If glasses are too tight or too loose, your child will be reluctant to wear them. Return to the optometrist that supplied them, or pop along to see our department’s dispensing optician to get the glasses adjusted to fit comfortably.

With very young children and more active older children, adjustments are often necessary and required frequently. Don’t be embarrassed to keep asking your optometrist to adjust the glasses – they are very used to it!

Contacts and further information

Please do not hesitate to contact any of the following between 09:00 – 17:00 Monday to Friday:

Orthoptists: 01223 216528
Dispensing Optician: 07809 721879 (Contactable any time)
Paediatric Ophthalmology Nurses: 01223 596414
Clinic 3: 01223 256691

All of the above have a 24-hour answer machine service.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

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Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151