A guide to Myopia
Myopia is the medical term for short-sightedness, which causes difficulty seeing objects in the distance. Myopia is a very common condition with most people developing symptoms during puberty, which gradually get worse over the course of time. Common signs of myopia include struggling to see words on a board at school and having difficulty reading signs in the distance.
Short-sightedness affects many people, though it is slightly more common in females than males, and is usually caused by a combination of genetic and environmental factors. It is uncommon for people to develop symptoms of short-sightedness after the age of 30, though older people may experience similar symptoms if they develop cataracts.
What causes myopia?
When light enters the eye it is focused by the cornea and lens, before hitting the retina at the back of the eye and being converted into electrical signals that are sent to the brain by way of the optic nerve. In order for the image to be clear the eye must be the right length and the cornea must be curved and shaped correctly. If the eye is too long the images will be blurred.
Most babies are born with slight short-sightedness but their sight can be corrected as their eyes grow. However, if the eyes continue to grow without treatment it can be difficult for light rays to reach the retina at the back of the eye, as the eye is longer than normal. However, if the rays of light do not reach the retina they will simply be focused before the retina, which causes the images you see to become hazy and unfocused.
It is not fully understood why some people have abnormally shaped corneas or eyes that grow too long. However, some risk factors have been identified:
- Family history and genetics: if you have a parent with myopia, you have a 40% risk of having the condition and the chances rise to 60% if both your parents have myopia.
- Detailed activities: reading and doing close-up detailed activities on a regular basis can increase your risk of developing myopia. However, reading is an important educational activity and should not be discouraged. If you do read a lot try to make sure you have plenty of light and rest your eyes occasionally.
Symptoms of myopia
Myopia causes images and objects to appear blurred with symptoms usually becoming worse over the course of time – but it can usually be eased by wearing glasses or contact lenses. Most people start to develop symptoms during puberty, but younger children can also experience symptoms. Many young children with myopia may assume that blurred vision is normal and they will not know that anything is wrong, until they go to school and find that they have difficulties reading the board from a long distance or reading signs from far away. Most people notice symptoms when they find it difficult to read road signs or posters in the distance or have difficulty seeing images on the television without being close to the TV set.
How is myopia diagnosed?
Myopia is diagnosed through an eye test and it is advisable to have eye tests regularly, even if you do not notice any symptoms. As myopia gets worse over time it is beneficial to see an optometrist as early as possible if you do experience symptoms, such as blurred vision and difficulty seeing objects in the distance. When you go for an eye test, your optometrist will examine your eyes and test your sight. If you do have glasses / contact lenses you should bring these to your meeting, because your sight will be analysed with and devoid of them.
Your optometrist will usually have the means to diagnose myopia through some simple sight tests, but they will need to carry out a test called a retinoscopy to determine the severity of the condition. A retinoscopy involves shining a bright light into the eye in order to find how the retina responds to the light. Your optometrist will also ask you to read some charts using different potency lenses to find how your vision is affected by different lenses.
Health professionals use a grading system to classify cases of myopia. There are three different classes: mild, moderate and high myopia. People with myopia are advised to attend regular eye appointments, as the condition can become worse and is linked to an augmented risk of more serious eye conditions, including glaucoma and retinal detachment (retina becomes detached from the back of the eye).
Myopia is classified according to a measurement called dioptres (D). The higher the measurement the more advanced the myopia. Myopia is classified as follows:
- Mild myopia: between -0.5 and -3 D.
- Moderate myopia: between -3 and -6 D.
- High myopia: more than -6D.
Regular eye tests are advised for adults and children even if you do not have any symptoms. Ideally you should have a test every 12-24 months, but you may be advised to go more frequently if you have a family history of eye conditions (especially glaucoma) or you suffer from diabetes. If you experience symptoms affecting your vision do not wait until the next scheduled eye test, see your optician as early as possible. Free eye tests are accessible on the NHS for children, people above the age of 60 and people who have a high risk of developing eye conditions.
Treatment for myopia
One of the main treatments for myopia is wearing glasses / contact lenses to correct your vision. They are custom-made for the individual to correct vision and lenses are manufactured based on prescription. Concave lenses are designed to right short-sightedness. Many people find that they need two different pairs of glasses as they get older, to help them see clearly up-close and in the distance; this is because the lens of the eye becomes less flexible as we get older.
Contact lenses work much like glasses do but the lenses are placed directly into the eye. A lot of people opt for contact lenses since they cannot be seen by other people. If you do wear contact lenses it is imperative that you have good eye cleanliness to prevent infections. There are various types of contact lens available, including soft lenses and rigid gas-permeable lenses. Also, you can also select from daily lenses which are binned at the end of a day or lenses that are worn for longer.
Laser eye treatment
Laser eye treatment is becoming an increasingly popular treatment for myopia. The major benefit of laser eye surgery is that you should not have to worry about wearing glasses or contact lenses after the procedure and your sight will be much improved. Laser eye treatment is not ideal for all patients, but if you are interested in having laser treatment you should go for a consultation with a surgeon first. They will be able to examine your eyes and determine whether or not you are a suitable candidate for treatment.
There are three central variations of laser eye treatment:
- PRK (photorefractive keratectomy): this process requires the removal of a very tiny part of the outside of the cornea and re-shaping the cornea with laser beams to correct vision.
- LASIK (laser in situ keratectomy): this process involves making a very tiny incision and lifting a flap of the cornea to re-shape it using laser technology.
- LASEK: this is very similar to PR but alcohol is used to slacken the outside of the cornea before the lasers are used to re-shape it.
Laser eye treatment is thought to be a safe and effective treatment, but it does carry risks as with all procedures. Your surgeon will explain the risks before you agree to have the treatment.
Lens implant surgery
This is a relatively new procedure for treating myopia and involves implanting an artificial lens into the eye. The artificial lens is designed to compensate for problems with the cornea in order for light beams to reach the retina. Lens implant surgery is not usually available on the NHS.
Complications of myopia
If you have severe myopia you have a higher risk of developing eye conditions and it is important that you receive treatment as early as possible and attend regular eye appointments. Myopia can increase the risk of the following conditions:
- Retinal detachment.
- Macular degeneration.