Glaucoma

This resource has been written to explain:

• the way our eyes and brain normally work to make ‘vision’
• the reason why vision may become impaired by a specific condition
• the cause of the condition
• the effects of the condition on the child’s vision
• how the condition is diagnosed
• what can be done to help

This document is not a substitute for a consultation with a health professional and should not to be used as a means of diagnosing a condition.

This information is intended to describe most aspects of the condition but each child is different and there will always be exceptions.

How our eyes work

What we see is actually made in our brains. Our brain makes sense of what signals are sent to it by our eyes.

What is the normal structure of the eye?

The eye is made of 3 parts:

• a light focussing bit at the front (cornea and lens)
• a light sensitive film at the back of the eye (retina)
• a large collection of communication wires to the brain (optic nerve)

Eyes are pumped up with water

For our eyes keep their shape, they are pumped up with water. It is a bit like a football being pumped up and inflated with air. You can feel the ‘pressure’ in your own eyes by gently feeling them through your closed eyelids. The amount of pressure depends on the flow of water in and out of your eye. If the flow of water out of the eye becomes blocked, then the pressure goes up. High pressure in the eye can cause damage to the optic nerve.

What is glaucoma?

Glaucoma is when the optic nerve is damaged by high pressure in the eye.

What is the cause of glaucoma in children?

Water drains out of the eye through a narrow gap between the coloured part of the eye (iris) and the clear curved window at the front (cornea). Sometimes this narrow gap can become blocked. This leads to high pressure in the eye. Eye doctors often call the drainage gap the ‘drainage angle’ or ‘trabecular meshwork’.

There are many different causes of a blocked drainage gap

Some children are born with a thin piece of skin blocking the drainage gap. This is known as primary congenital glaucoma. Congenital means ‘to be born with’.

Other children are born with an open drainage gap, but later on develop a blocked drainage gap. This is known as secondary glaucoma. The drain becomes blocked in these children because of another eye condition. Common conditions that can also cause glaucoma include iritis or retinopathy of prematurity (ROP).

Why are some children born with a blocked drainage gap?

Most cases of primary congenital glaucoma happen by chance. Sometimes glaucoma can run in families. Sometimes it can run very distantly in families, with a distant relative having been born with glaucoma. This is called ‘recessive inheritance’.

There is a wide range of congenital glaucoma conditions

There is a wide range of congenital (born with) glaucoma conditions.

Some conditions only affect the trabecular meshwork where the water in the eye drains out at the drainage gap.

Children with glaucoma usually only have problems with their eyes. If a child has glaucoma they may also other conditions as well. A child is more likely to have other conditions if the iris and pupil are affected as well.

In other children the iris can show obvious changes as well. They may have extra pupils or an unevenly shaped pupils. This is called Reiger’s syndrome. A child may also have a flattened appearance to the nose and face. They may also have fewer teeth than normal. Very rarely they may also have poor hearing, learning difficulties and problems with their heart.

Sometimes the iris is missing altogether. This is called aniridia. Some children with aniridia can develop tumours in their kidneys. They may need regular scans to look for this.

How does glaucoma affect the eyes and vision of children?

Sensitive to bright light

Children with glaucoma sometimes do not like bright light or going outdoors. This is called photophobia.

Their may also water constantly and look larger than other children.

If the pressure in the eyes is very high, the cornea may look hazy and not as clear as usual. If you notice these signs, ask your family doctor to arrange an examination by an eye doctor. If the pressure is lowered then the cornea usually becomes clear again.

After the cornea clears small ‘cracks’ on the inside surface of the cornea might still be seen. They are called Haab’s striae and do not usually affect vision.

The damage to the optic nerve from the high pressure however does not initially cause any problems with vision. If the high pressure is not treated, the optic nerve can become damaged and get worse. Your child may slowly develop hazy vision that creeps in from the edges and cause blurry vision.

High pressure in an eye of a child can also make the eye grow bigger than usual. This is called ‘buphthalmos’. Children with bigger eyes are more likely to need glasses to see clearly. Children with buphthalmos are also more likely to develop a squint or lazy eye.

How is glaucoma diagnosed?

Glaucoma can be diagnosed during an eye examination. Your child’s eye doctor will:

• check pressure in the eye
• looking at the drainage angle
• looking at the optic nerve

If the pressure in your child’s eye is high, then they will likely have glaucoma.

Sometimes they use a small mirror to look at the drainage angle. Water in the eye drains out at the drainage angle. In glaucoma it can often look different to usual. If the angle looks blocked or not fully developed then this might explain why the pressure is high.

The way the optic nerve looks can also help to make a diagnosis. In glaucoma damage occurs to the optic nerve. This causes some of the wires within it to wear out and disappear. By looking into the eye with a special instrument all these wires can be seen ‘end on’ as they exit the eye and pass to the brain. This is the ‘head’ of the optic nerve. If none of the wires are damaged then the ‘head‘ of the optic nerve looks yellow and pink. If many wires are missing then the optic nerve looks pale and white. This is the common appearance in glaucoma. Eye doctors often describe the damage to the optic nerve head as ‘optic disc cupping’.

Younger children can be difficult to examine when awake. It is easier while they are asleep, under a short anaesthetic. While asleep the eye doctor can check the pressure in the eye and the appearance of the head of the optic nerve. Most young children will need to have this 1 or 2 times a year.

What can be done to help?

If the pressure in the eye is lowered the damage to the optic nerve usually stops. The pressure can be lowered by several different kinds of operation. All the operations work by trying to increase the flow of water out of the eye. This usually helps to lower the pressure and prevent further damage to the optic nerve.

If a skin is blocking the drainage gap of the eye it can be cut open. This is called a goniotomy. This allows more water to drain out of the eye and lowers the pressure. If this does not work other kinds of operations can be done (such as trabeculectomy or drainage tube insertion). Sometimes drops can also be given to help lower the pressure.

How can I help my child?

Make sure that your child attends all their appointments, and follow that any treatment as instructed.

If your child has been prescribed glasses, contact lenses or a low visual aid (LVA) it is important that they are encouraged to wear and use them. This will help your child see more clearly and make sure the parts that are working well, continue to grow and develop correctly.

Be aware that adjusting to daylight in the morning can be uncomfortable. Sometimes this is painful and the eyes may water a lot. Be aware of the problems with glare. Children may need reduced or shaded light. Blinds and curtains are useful. Wearing a hat and tinted glasses can also help reduce symptoms of photophobia. Wherever possible use matte surfaces for desktops, whiteboards, paper, wall, floors and so on. Shiny surfaces, snow and water can reflect light causing glare.

If your child has also been prescribed drops they should be used regularly as advised by the nurses and doctors at the eye clinic.

We use our vision to get around, learn new things and to meet other people and make friends.

Most children with glaucoma have few problems getting around. The way they act can give the impression that their vision is normal. It is important however to be aware of their own special problems with vision.

Problems at school may be due to some of the reading books being hard to see. This often means it takes longer and more effort to do the work. If the size of print is increased most children will find schoolwork easier, especially if they also use their LVA. If a child has been given an LVA then they should be encouraged to use it.

• Near work – a close reading position may be preferred and should not be discouraged.
• Seating in school – where possible the child should be seated close to the teacher, away from windows if there are no blinds and close to the board and television.
• School equipment – children may benefit from using some type of magnifier. This enlarges print making reading less tiring. It may sometimes be helpful to provide a desk stand or a copyholder, which will bring work to eye level and prevent discomfort and poor posture.

It is worth watching carefully to find out what the smallest toys are that a child can see and play with. Then try to only play with toys that are the same size or bigger.

Recognising facial expressions can often be difficult. It is worth trying to find out at what distance facial expressions can be seen and responded to. Then always try to talk and smile from within this distance. This helps a child to learn what facial expressions mean and to copy them.

Even if your child has very poor vision many useful and practical things can be done to help.