Glaucoma is thought of as a disease of adulthood with a greater risk as one ages and this is largely true. However glaucoma can strike at any age and sometimes it affects children.
Early onset glaucoma arises because of an inborn abnormality of the structure and/or function of the pressure drainage area in the eye, the trabecular meshwork. Depending on the severity of the abnormality it can be present when a baby is born or it can arise later. When glaucoma occurs under the age of three we call it infantile glaucoma and if after the age of three then it becomes juvenile glaucoma.
A lot of the glaucoma seen in young people is secondary, meaning that some other disease or condition has caused it. This includes, for example, another type of inborn eye problem, an injury or inflammation in the eye. Children who are born with cataracts that require removal within the first few weeks of life can develop glaucoma. This means any child who has cataract surgery must be kept under glaucoma surveillance by an ophthalmologist or optometrist for the rest of his/her life.
Infantile glaucoma behaves quite differently from the glaucoma seen in older people. The cornea, the window portion on the front of the eye, has a far greater tendency to become cloudy (oedematous) and this leads to watering and light sensitivity. Sometimes that watering leads to a misdiagnosis of a blocked tear duct. A young eye is relatively soft so any pressure rise can cause the eye to enlarge (buphthalmos), something that doesn’t occur after the age of three.
The optic nerve in children can be more tolerant of elevated pressure than an adult nerve but on the other hand even a slow worsening is more relevant when your eyes have to last 70-80 years rather than 20-30.
When glaucoma causes loss of nerve fibres we see increased cupping of the nerve, meaning that the depression in the centre of the nerve head in the eye gets larger as the rim of nerve fibres gets thinner. In children and young adults some of that cupping may be reversible with the cup getting smaller again, and the nerve rim improving, as the disease is brought under control. This occurs because the less rigid eye of a child allows some outward bowing of the nerve which makes it look more cupped. When the pressure comes down the outward bowing reverses and the cup size gets smaller again. This can be seen in people as old as 35.
The treatment of infantile glaucoma is also very different with surgery being the primary therapy and drops more as an adjunct. Different types of surgery may be appropriate in children including goniotomy, which involves using a needle inside the eye to try to open up the trabecular meshwork so it can work more efficiently. This is usually very effective but is less so when the glaucoma is due to some other disease than when it occurs on its own.
The surgeon needs to be able to see into the eye to perform goniotomy and if this isn’t possible then trabeculotomy is the other option. This should not be confused with trabeculectomy which is the standard adult glaucoma operation. With trabeculotomy a flap is created on the sclera (the white of the eye) and the channel that drains pressure from the trabecular meshwork is identified. A probe is passed along this channel and then rotated into the eye. You can think of trabeculotomy as creating a pathway from the outside in and goniotomy from the inside out.
Glaucoma eye drop use in children is different from adults with fewer options available. For example Alphagan (Brimonidine) can cause sleepiness and affect breathing and is usually avoided in children under eight years of age. If babies are treated with Timolol drops then they should sleep on an apnoea mattress as this drop can affect breathing.
Monitoring eye pressure in young children can be challenging and full assessments sometimes require repeated general anaesthetics. However, most of the time, with the equipment available nowadays, the checks can be done in the clinic. Of particular value in measuring the pressure is the i-care tonometer which can be used without even putting anaesthetic drops in the eyes, a real bonus when dealing with children. In fact it is remarkable how well some young children manage their eye checks; even at three or four some will sit on Mum or Dad’s lap and happily put their chin up on the microscope for the examination.
A unique problem with paediatric glaucoma is the fact that the vision in children is still developing until around eight years of age. Any eye condition that interrupts normal vision, including glaucoma, can slow that development and cause laziness of the vision (amblyopia). We can treat that with patching of the better eye but sometimes it is difficult to reverse and in fact more children with glaucoma lose vision from amblyopia than from optic nerve damage.
Paediatric glaucoma is quite different from adult disease and its management has some special challenges. On the other hand, as is usually the case when dealing with young people, the visits can be fun and the satisfaction of helping a young child maintain vision for a lifetime is particularly rewarding.