Eye Info

High Degree Myopia

Summary: Designed to help you understand more about your eye condition, this guide has been written by our experienced eye health team.

• What is Myopia?
• What are the effects of the condition?
• How can myopia be treated?
• Are there any risk groups or does myopia run in families?
• Other sources of support
• What's next?

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What is Myopia?

Short-sightedness, or myopia, is a vision problem resulting from excessively long growth of the eye-ball, or a steeply curved cornea. Myopia up to 3.0 dioptres (D) is termed mild degree, 3.0 to 6.0D is moderate degree and high degree is 6.0D and over. A dioptre is a measurement of the focusing power of a lens.

Most commonly, myopia will stabilize when the growth process has been completed and will result in normal sight after correction with glasses, for example.

High degree myopia (sometimes known as pathological myopia or degenerative myopia) is a chronic, degenerative condition which can create problems because of its association with degenerative changes at the back of the eye.

What are the effects of the condition?

Myopia causes light rays to focus on the front of the retina and so close objects are seen clearly whilst distant objects appear blurred.

Near vision can deteriorate to a level where even very close to the face become hard to focus.

There is a slight danger of sight loss since the deformation of the eye creates stress on the retina which can become damaged or detached and can also provoke other changes. This is especially the case in high myopia.

How can myopia be treated?

Although there are procedures for stabilising the myopic eye, treatment only addresses the symptoms and no cure is available.

Traditional correction of this refractive problem is by glasses or contact lenses. Additional refractive problems, such as astigmatism, or curvature of the eye, can be corrected in the same way.

Some people, either for cosmetic reasons or reasons associated with their work, have wanted to "cure" their myopia surgically. Until the 1990s, if myopia was treated it was by a surgical procedure called radial keratotomy.

More recently laser surgery (photorefractive keratotomy or PRK) has become popular. The operation takes about 15 seconds and the entire procedure usually lasts about 15 minutes. This procedure is only available privately at present. It is of most use in low degrees of myopia. The long term results are still not known.

Surgical correction of myopia is rarely offered on the NHS and when offered will involve a series of small incisions designed to flatten the cornea and redirect focus on to the retina. Laser surgery is offered through a rapidly increasing private sector specialist to this work. Until long term trials have established its acceptability, laser correction will not be available on the NHS.

Over 15,000 people have already received PRK in Britain. The majority of people do well and are completely satisfied although others require two or three treatments during the initial six month period before a satisfactory conclusion is reached. There is considerable pain for two to three days following surgery.

Clinical trials identify problems which can arise from the procedure. These include deteriorated night vision, light scatter and haloing, cloudiness as well as the necessity to have repeat surgery.

Very rarely, in some cases where serious damage occurs, a corneal transplant is needed. The cornea is the transparent membrane at the front of the eye.

Best results occur in the range up to 6 dioptres.

Are there any risk groups or does myopia run in families?

Around 5 million British people are short sighted and some 200,000 of them will have high degree myopia. In a few people, high degree myopia might cause retinal damage or detachment. It may be associated with cataract and glaucoma.

High degree or chronic degenerative myopia can run in families and it might be advisable to discuss this with your medical advisors. You may also contact a Genetic Centre or seek referral from your GP or eye specialist.

Other sources of support

RNIB is not aware of a specialist group offering support and information for people with myopia but is happy to discuss problem solving services available from RNIB and other organisations designed to meet individual needs.

What's next?

Our Adapting to sight loss page gives information useful for people with a newly diagnosed sight problem.

If you need more information contact our Helpline on 0845 766 9999 / helpline@rnib.org.uk - calls are charged at local rates.

RNIB does not comment on every trend or development but, when a treatment becomes established / recognised, we revise our website material to include it.

Unfortunately, RNIB can only answer email enquiries from the UK. But you may find an organisation for people with poor sight in your country through our agencies database.

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Content author: eyehealth@rnib.org.uk

Last updated: 06/03/2008 15:41