A child recently attended the practice complaining of problems reading the blackboard, and his parents asked whether he was short-sighted or long-sighted. The main symptom of myopia (short-sightedness) is distant objects appearing blurred, while near objects can still be seen clearly. People who are short sighted sometimes suffer from eyestrain and headaches, especially after long periods of driving or concentrating on TV.
When does it start?
Myopia usually appears around puberty, often after a growth spurt. However, it can appear at any age from early childhood up to 25 years of age.
Usually, the degree of myopia increases with age because the eyeball grows as the child grows. In most cases, myopia stops intensifying when the person stops growing. In older people, the onset of myopia can be the earliest indication that a cataract (cloudy lens) is starting to form. Some children who develop myopia may not realise at first that their vision has been affected. They may be able to read books and do close work well, but may find it difficult to see distant objects, such as the blackboard at school. Often, they think this is normal and do not tell anyone.
Short-sightedness is caused by an abnormality in the shape of the eyes. A ‘myopic eye’ is either too long from back to front, or the cornea or lens is too strong. This leads to a mismatch between focusing power and eye length, resulting in the light rays from the object not reaching the retina and the resultant images not being in focus.
There is a tendency for myopia to run in families, although it is believed that a number of factors combine to cause myopia. A person’s genetic make-up and the environment they grow up in are considered to be linked to the development of myopia. Children have an approximately 30 per cent chance of developing myopia if one of their parents has the condition, and a 55 per cent if both have it.
People who spend a lot of time reading, working at a computer or doing other close-vision work may develop temporary myopia (where vision returns after resting the eyes). Also, they may be more likely to develop permanent myopia. Blurred vision can also be a symptom of other health problem, such as diabetes.
An optician will usually diagnose myopia after a sight test. Children may have their vision checked at school. If not, parents should book their children for a sight test with an optician.
Children should have their sight tested at least every year. Parents of children who may be slightly more predisposed to myopia (they have a strong family history, for example) should be extra observant during ‘growth spurts’.
If you have severe short-sightedness (high-degree myopia) you are more likely to develop eye disorders in later life, such as retinal detachment, glaucoma and cataracts.
Patients with myopia over 5 dioptres are more predisposed to retinal detachment – signs include floaters and flashing lights. If you experience any of these signs please make an appointment with your optician as soon as possible.
Áine Higgins is an Optometrist based in Mongey Opticians Castlebar and Ballinrobe – She was the first Irish Optician to be awarded Optician Of the Year UK and Ireland 2010.