Refractive errors
All three conditions are referred to as ‘refractive errors’. This means the shape and length of the eye is distorted, which affects the bending of light as it focuses on the eye’s retina – known as ‘refraction’.
Most refractive errors occur within a defined range of optical power. Outside this range, the error is considered high, as in ‘high myopia’ or ‘high hypermetropia’. These high errors usually indicate that other medical problems within the eye may occur more often. People with refractive errors are likely to suffer decreased vision, eye strain and discomfort, and occasionally headaches.
Types of refractive errors
At Medownick Laser Eye Clinic we can treat all three conditions separately, or in combination, to provide you with the maximum improved vision.
Myopia (short- or near-sightedness)
Myopia comes from the Greek word for ‘closed eyes’. If you have ever squinted to see something in the distance, you’ll agree this is a good representation of how to describe the condition, as the eye is able to see close objects but has trouble bringing distant objects into focus.
What you see if you have myopia
Physically, the myopic eye is more oval than round, meaning there is a longer distance from the front of the eye to the back. As a result, the lens is unable to focus light from distant objects clearly on to the retina. Myopia can also be caused by a distortion in the shape of the cornea or lens, although this is rarer.
Myopia is an inherited condition, and is often detected in children as young as two to 12 years old. Typically, the eyes will get worse during the teenage years, but level off upon adulthood. To keep up with the changes in sight, new glasses may need to be prescribed every six months or so. Between the ages of 18 and 40, your eyes stabilise and your prescription won’t change a huge amount – this is the best time to consider laser eye surgery.
Hypermetropia (long- or far-sightedness)
If you can see objects in the distance well, but have difficulty viewing them up close, you have hypermetropia. This condition occurs when the distance between the cornea at the front of the eye to the retina at the back of the eye, is shorter than normal.
What you see if you have hypermetropia
Like myopia, hypermetropia is usually inherited. It is found in the eyes of most young children to some degree, and is associated with ‘crossed eyes’ in children, since the muscles of the eyes have to contract tightly to see objects up close. In a lot of cases, however, as the eye grows, the hypermetropia can ‘fix’ itself.
If it does progress into adulthood, and you are experiencing long-sightedness, laser eye surgery may be able to correct your vision.
Astigmatism (blurred or distorted vision)
Astigmatism distorts or blurs vision for objects at any distance – short, mid or long distances – and often occurs in conjunction with myopia and hypermetropia. For normal vision, the cornea should be smooth and equally curved in all directions like a perfect sphere. If you have astigmatism the cornea is warped, meaning it curves more in one direction than the other and is a bit like the shape of a football or an egg.
What you see if you have astigmatism
As with myopia and hypermetropia, high astigmatism is usually inherited. It is usually evident from birth, and will require some form of vision correction, typically glasses. Low-level astigmatism is also very common and can occur any time during our lives. It generally does not require corrective lenses unless it occurs with myopia, as it often does.
If you have astigmatism, laser eye surgery can help. Our laser is very effective in treating astigmatism.
Next: Presbyopia
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