Common Eye Conditions

Refractive Errors

Hypermetropia (long sight)

This is caused by the eye being optically too small, so that the rays of light entering the eye focus behind the retina (back of eye) instead of on the retina. A certain amount of long-sightedness is normal in childhood. Long sighted children may have reduced vision for near and distance depending on the amount that has been identified, although it is more usual that near vision is affected.

Myopia (short sight)

This is caused by the eye being optically too large, so that the rays of light entering the eye focus in front of the retina instead of on the retina. Short sighted children may have a ‘clear point’ for near vision, distance vision is affected much more.
 

Astigmatism

In addition to being long or short sighted, your child’s eyes may be of irregular shape, commonly compared to the shape of a ‘rugby ball’ and, as a result, vision is affected further, both for near and distance.

Amblyopia

Amblyopia is the medical term for a “lazy eye”. The reduced vision in an amblyopic eye occurs even though there is no structural abnormality of the eye. Amblyopia is responsible for more visual loss in childhood than all the other causes of visual loss combined.

What are the causes of amblyopia?

• Strabismus (squints) - when a child develops a squint their brain is able to ‘turn off’ the image from one eye, preventing them from experiencing double vision. This process is known as suppression. As a consequence of suppressing the image from one eye the connections between this eye and the brain do not develop in the normal way and the vision in this eye is reduced. This is known as strabismic amblyopia, because it has arisen as a result of a squint.
   
• High refractive error in both eyes - both eyes may be significantly longsighted/shortsighted and one or both eyes may have a high degree of astigmatism. These conditions can result in amblyopia because of the blurred image they produce.
   
• Unequal refractive error (anisometropia) - the other common cause of amblyopia is when there is a significant difference in refractive error between the two eyes. The medical term for this is anisometropia. This means that the more long or short sighted eye will be seeing a blurred image, compared to the fellow eye and the brain will choose to ignore this blurred image.
   

Why is it important to improve the vision in the amblyopic eye?

In children who have the potential to develop stereopsis, their 3D vision will be better if they have good vision in both eyes. Perhaps the most important reason for treating amblyopia is to ensure that the vision is good enough in the amblyopic eye to enable the person to drive a car, work and live independently if they were to lose the vision in their other eye in later life.
 

Squint

A squint or strabismus refers to a misalignment of the eyes. There are many different types of squint, but broadly speaking they can be divided into the following groups:

• Esotropia - the medical name for a convergent squint where one eye turns in towards the nose.
• Exotropia - the medical name for a divergent squint where the one eye turns outwards.
• Hypertropia and hypotropia - refer to vertical squints where one eye is higher (hypertropia) or lower (hypotropia) than the fellow eye.

So there are many different types of squint and treatment will vary accordingly. The eye that turns may well have reduced vision and is often called ‘lazy’. A squint can be caused by the need for glasses, although sometimes there is no obvious reason.

A child does not usually grow out of a squint. Treatment is similar to that of anisometropic amblyopia, with glasses and patching used to achieve best vision.  If the squint is cosmetically poor surgery may be required.

 

Occlusion (patching)

By covering the good eye for part of the day we force the ‘lazy’ eye to work harder.

The amount of patching needed depends on the child’s age and level of vision.

This will be carefully monitored by the orthoptist.

Eye drops (atropine sulphate 1%) can be used as an alternative to patching.

By putting atropine in the good eye a couple of times per week, it temporarily blurs the vision, forcing the lazy eye to work harder.

 

Myopia and its management

Long periods of near activities – reading and screen use may affect how myopia develops. Research shows that spending time outdoors may help prevent or delay increases. Myopia is usually corrected with glasses or contact lenses.

Due to its nature myopia usually increases slightly with growth. Trying to slow down how quickly it increases is known as myopia management.

Current evidence suggests that using special contact lenses or specially designed glasses may reduce the progression of myopia by 40-60 per cent.  This reduction is usually seen over 1-3 years but most of the benefits are seen early on.

The treatments work by changing how light is focussed on different parts of the retina whilst providing clear vision.

The glasses look the same as standard glasses and are worn in a similar way to ‘normal’ ones.
Contact lens treatment is only recommended if your child is old enough to be able to use and look after their lenses.

Advantages of myopia management:

• may slow down rate at which myopia develops by 40-60%
• may be lower risk of myopia-related eye problems in later life
• Risk complications from wearing contact lenses

Disadvantages of myopia management:

• some peoples vision may be slightly blurred during treatment
• have to pay as treatments are not available on the NHS
• myopia management glasses/contact lenses are more expensive than standard ones