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What are refractive errors?

Refractive errors such as myopia, hyperopia, presbyopia and astigmatism are very common problems of the eye. Most of the people have one or more of them and, in general, then can be easily corrected with glasses or contact lenses.

Myopia, hyperopia and astigmatism are caused by differences in the longitude or shape of the eye. Presbyopia, in turn, happens when the crystalline lens loses its capacity to focus on objects that are near you due to age.

We call all these conditions "refractive errors" because the eyes affected cannot properly focus the objects on the retina.

The main symptoms of refractive errors are blurring of vision, itch, feeling tension in the eye and, occasionally, headache. These last ones are caused by a continued overstraining. These symptoms tend to disappear when the defect is corrected, either with glasses, contact lenses or surgery.

What is Myopia?

Myopia happens when the eyes can "recognise" objects that are close properly but cannot clearly focus them from a distance. It consists of a refractive error that is generally detected during childhood.

From the moment it is detected until 20 years of age, myopia can increase, sometimes at such a fast rate that glasses need to be changed very frequently. After 20 years of age, there are less and slower variations. Reading a lot, poor lighting, nutritional issues or using contact lenses do not cause myopia or influence its evolution.

Myopias with more than 6 dioptres are considered to be "high" and require a regular monitoring of the retina since they are more likely to suffer from retinal detachments than a normal eye.

What is hyperopia?

In hyperopia, the eye is shorter than usual. Therefore, the objects that are close cannot be focused on the retina, but behind it. It can also be caused when the cornea is too flat or the crystalline lenses are too thin, but this is less frequent.

Every child, when born, tends to be farsighted, to a higher or lower extent. When the eye grows and enlarges, hyperopia decreases or disappears.

Sometimes, hyperopia in children is related to a certain degree of strabismus due to a lack of coordination between the ocular muscles which have to make constant effort to focus the objects that are close.

Headaches, red eyes and lack of interest in reading are frequent. In children, it is necessary to correct hyperopia as well as any other refractive error capable of decreasing vision, no matter how tiny it is.

What is astigmatism?

For a normal and undistorted visión, the cornea has to be smooth and have a curve similar in all directions. In people with astigmatism, the cornea is more curved in one direction then in the other. In general, astigmatism causes a blurred or distorted vision for objects placed a a certain distance. We could compare it to the images seen in mirrors where people see themselves too tall, too short or too thin. Generally, astigmatism is hereditary and it happens to young people. It does not tend to change throughout life. Frequently, astigmatism is mild and it does not always require correction. In other casesm corneal astigmatism can be the consequence of a previous surgery.

What is presbyopia?

If you have presbyopia, you lost your ability to focus, which generally happens when ageing.
Most of the people are between 40 and 50 years of age when they realize they are losing the ability to see objects or read what is close to their eyes.

Optical Correction Methods

There are several optical methods to correct presbyopia: monofocal glasses, bifocal glasses, multifocal glasses and contact lenses.

Refractive Surgery

Many people with refractive error do not want to depend on glasses to perform any activity. Not all of them think contact lenses as a solution.

Special circumstances such individual activity, sports or a physical or psychic intolerance to contact lenses make them think of surgery. Not all refractive problems or all people can undergo this type of surgery.

After a careful examination of the patient, the ophthalmologist will finally determine is undergoing the surgery is advisable and what type of intervention it will be.

Surgical Technique

This surgery lasts 10-15 minutes approximately and it does not cause any pain.

The procedure we currently use is laser-assisted keratomileusis.

The aim is shaping the anterior corneal surface to correct the refractive defect of the treated eye.

The decision is also based on other factors such as: age, profession, sport activity and ophthalmological examination of both eyes.

After a careful examination of the patient, the ophthalmologist will finally determine is undergoing the surgery is advisable and what type of intervention it will be.