As soon as there are any changes to either the smooth, spherical surface, or to the clarity of the cornea, the light can no longer pass into the eye in a uniform manner. The rays hit the retina at odd angles and so a distorted image is created. The more severe these changes, the more erratic the path of light to the retina and the worse the vision becomes.
In Keratoconus, the cornea starts to stretch outwards in a cone shape too and as it does so, it becomes thinner. The surface becomes “bumpy” or irregular. You can imagine that light having to pass through all these changes to reach the retina, is going to have a pretty tough time of it.
To help you visualise this process, think of stretching out a blob of prestik or chewed chewing gum. The further you stretch it, the thinner and weaker the strand becomes. It starts to bow towards the ground in a cone shape.
WHAT IS THE CHANCE OF MY CHILD HAVING THIS CONDITION AND WHEN DOES IT START?
Did you know that near-sightedness can be caused by keratoconus?
The figures vary from country to country, but the most agreed upon percentage is 5%. That means that in every 20 children one of them may suffer from this condition, so it is more common than you would think.
Keratoconus usually becomes evident in children in their teens to early adulthood. It is rare to find a child presenting before puberty. It affects both eyes, but not at the same pace. The condition progresses until the child reaches their mid thirties and then it stabilises.
ARE THERE ANY CONDITIONS THAT MIGHT PREDISPOSE MY CHILD TO KERATOCONUS?
Children with asthma, hay fever and eczema may develop keratoconus
There are a few that may signpost you to this condition.
The first is to look into your family tree. A high proportion of keratoconus sufferers have a genetic link causing their condition. The gene is thought to be inherited in a dominant fashion, but the way in which it presents may vary.
So a relative may have mild vision disturbances and not realise that they have this condition. Conversely, a family member with the same gene may experience severe vision loss. It is worthwhile finding out about your family’s “vision” history.
There are other genetic conditions that may put your child at risk, such as Down’s syndrome and Marfan’s.
Children with eczema, hay fever and asthma are also at risk. This is for ‘mechanical’ reasons. As their eyes are frequently itchy, they tend to rub their eyes a lot. This continual pressure stretches and thins the cornea, rather like rolling out cookie dough with a rolling pin. The end result is keratoconus.
WHAT SIGNS SHOULD I LOOK OUT FOR?
As the passage of light into the eye is being disrupted, your child may complain of blurry vision, double vision, nearsightedness, halos forming around a light source and light sensitivity.
If your child has asthma, eczema or hay fever, be aware of how frequently they rub their eyes.
In severe cases, you may notice that the clear cornea has become hazy or even opaque and there may be scarring.
IF I SUSPECT THAT MY CHILD MIGHT HAVE THIS CONDITION, WHAT SHOULD I DO?
Your child will need an eye examination. This can be done by an optometrist who can then refer you and your child on to an ophthalmologist specialising in keratoconus or a paediatric ophthalmologist.
You can reasure your child that the examination is not painful and that the most uncomfortable examination they will be exposed to is having a bright light shone into their eyes. Plan to book the appointment at a time of day that your child isn’t typically tired and ensure that they have eaten before being assessed.
HOW IS KERATOCONUS DIAGNOSED?
The shape of the eye changes from that similar to a tennis ball to the shape of a rugby ball
Both eyes are carefully examined with a specialised hand-held light called a retinoscope and then with a slit lamp to check for signs of this condition.
Specialised digital pictures are taken of the cornea to determine the unevenness and curvature of its surface. This is called corneal topography. The advantage of this process is not only to create a precise map of the corneal surface and shape to aid diagnosis, but to assess the progression of the disease as images from one visit can be compared with those of past assessments.
WHAT IS THE TREATMENT FOR THIS CONDITION?
The type of treatment prescribed will depend on the severity of the disease.
In mild and moderate cases, eye glasses and or contact lenses may improve vision and reduce glare.
In severe cases, a procedure called collagen cross linking with Riboflavin, has been a major break-through. In most cases it slows down the progression of the disease by preventing further coning of the cornea.
In extreme cases where cornea scarring and haziness is noticed, a corneal transplant can be offered, but it is better to wait until the child is an adult. This is to ensure that the disease has stabilised and that there won’t be any further changes in the eye that could adversely affect the outcome of surgery.
Counselling is a vital component in the treatment of keratoconus. As the disease is progressive, the child will experience worsening of their vision as they age. This is distressing and frustrating. They may need frequent check-ups with regular changes in their spectacle or contact lens prescriptions.
Depending on the severity of the condition, they may miss out on fun activities that their peer group is involved in such as playing sport and may experience teasing.
Future career options also need to be addressed as their worsening vision may limit their options.
Early diagnosis and treatment certainly improve quality of life and help slow the negative effects of the disease.
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Children Can Have Keratoconus
- Oxford Handbook of Clinical Medicine, Second edition, by A. O. Denniston and P. I. Murray. Pages 230-231