Short and long sight
Short-sighted (myopia) is a condition where you can see close objects clearly, but those in the distance are blurred. It occurs when the power of the cornea is too strong or the eye is too long, so that light entering the eye, focuses in front of the retina.
The condition is relatively common in the UK, affecting approximately one in five adults. It usually develops as an older child or a teenager and stabilises by the time you are twenty.
Myopia in childhood
Short-sightedness can develop at any age and in children tends to get worse as they grow.
The younger they are when they start becoming short-sighted, generally the faster their vision deteriorates and the more severe it is in adulthood.
There is no single treatment available that appears to stop this progression. However, research has shown that atropine eye drops can slow the progression of short-sightedness, but it can cause side effects at high strengths – such as difficulty reading and sensitivity to bright light – and low-strength drops aren’t commercially available in the UK.
Orthokeratology and bifocal contact lenses may also slow down short-sight progression in children, but possibly not as much as the eye drops.
Long-sightedness is a confusing term since long-sightedness can affect people very differently at depending on the degree of long-sightedness and the age of the patient.
Clinically long-sightedness is known as Hyperopia; it is when the cornea is too flat, or the eye is too short, so light focuses, ‘behind’ the retina.
With a smaller degree of hyperopia, we may be able to overcome this defocus with help from the ciliary body which changes the shape of the lens and pulls the focussed light onto the retina. This can create clear vision in the distance.
The older patient or a patient with a higher degree of hyperopia, will not be able to overcome this defocus. Long-sightedness is very different to ‘presbyopia’ where we lose the ability to see near objects, when our eyes are fully corrected for distance.
Hyperopia in Childhood
If children have long sightedness, they can start to ‘squint’. It is important that all children have a sight test in early childhood, to check each eye and exclude undetected long-sightedness. This is often organised at your child’s school.
As we get older, the lens within our eyes starts to lose its ability to change its shape in order to alter its focus from distance vision to close vision. This natural ageing process is called presbyopia and it is unavoidable. This will mean that reading glasses are required. If we already wear glasses for distance, this will be in addition to our current glasses. Some people get success from contact lenses, which can reduce the dependence on reading glasses.
Astigmatism occurs when the eye is a less rounded shape than usual. Often referred to as being shaped more like a rugby ball (toroidal) rather than a football (Spherical). Astigmatism is created when the cornea of the eye has two different degrees of curvature, one steeper and one flatter which makes it impossible for the eye to focus light perfectly onto the retina.
People with astigmatism will often be able to see vertical objects clearly but horizontal ones may be blurred, or vice versa. Astigmatism is a common disorder, which often co-exists with short or long-sightedness.