Refractive Errors: Types, Symptoms, Treatment

Refractive errors are those conditions of the eyes that affects the ability of the eye to see images properly, as a result of poor focusing of image. When this happens, the individual would start experiencing blurred vision or eye strain. The main types of refractive errors are long sightedness (hyperopia), short sightedness (myopia), astigmatism and presbyopia (loss of near vision with age).

Refraction means the power of the eye to focus on an object and see its image clearly. In order to see clearly and for the image to be as sharp as possible, there are a lot of events that happens in the eyes that makes this possible. we cannot talk about this complex series of events here, to avoid boring you.

You know how your camera works? At least your phone camera. You notice how blurred the images are when you are not able to focus it properly on the object, whose picture you want to take or when your hands are not steady as you want to take the shot? That’s exactly what happens in an eye that has any form of refractive errors. The persons vision would be blurred and he/she would be seeing objects just like that image you took.

WHAT ARE REFRACTIVE ERRORS?

You suddenly notice that you can no longer read the prints on your phone without moving it farther from your face, or the writings on billboards are difficult to read or using your system has increasingly become problematic because you have headaches when you use it. Relax, don’t get worked up, you just might have a refractive error.

A refractive error is when the eye cannot focus images properly, leading to an individual experiencing blurred vision or eye strain.

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Causes of Refractive Errors

The causes of refractive errors depends on the type of refractive error. This can be due to the eyeball being too long (as in short sightedness), or the eyeball being too short (as in long sightedness), or other possible causes. See the types of refractive errors below, their causes and symptoms.

Refractive errors
Different types of refractive errors. Image Credit: Stereo Optical

Symptoms and Types of Refractive Errors

There are different types of refractive errors, and their symptoms differ.

Near/Short sightedness or Myopia

This is when rays of light entering the eye focuses in front of the retina instead of on it. It usually occurs because the eyeball too long or the cornea (front surface of the eye) is overly curved and/or the lens has a higher than normal optical power. This causes images coming from a distance to appear blurred.

Persons with this refractive error find it difficult seeing things that are far (distant objects or writings) clearly, but they can see those that are near and so might squint a lot and like to move very close to objects or bring them very close to their face.

Far/Long sightedness or Hyperopia

This is when rays of light entering the eye focuses behind the retina instead of on it. This usually occurs because the eyeball too short or the cornea is not curved enough and/or the lens has a lower than normal optical power. This causes near images to appear blurred.

Persons with this refractive error usually experience eye aches, headaches, eye fatigue, tearing etc, when doing near work like reading, writing, and computer work. They also tend to squint to see near objects but they can see those things that are far. They may also sometimes have poor distant vision.

Astigmatism

This is when the cornea or the lens in the eye is unevenly curved, causing rays of light entering the eye not to form a single focus on the retina. Typically, the cornea and lens are smooth and curved equally in all directions, and this helps focus light rays sharply onto the retina. But in astigmatism due to the uneven surfaces, rays of light entering the eye end up scattered with several focal points.

Persons with this refractive error experience blurred vision at both distance and near. They also experience intermittent periods of clear and blurred vision as the eye struggles to bring the scattered rays of light to a single point. But that extra effort to form a single focus cannot be sustained leading to periods of blurred vision. They are also prone to headaches.

Astigmatism can occur on its own or in combination with myopia or hyperopia

Presbyopia

This is a gradual reduction with age in the ability of the eyes to focus at near. This is because, over time, the lens of the eye which is responsible for focusing at near loses its elasticity and thus its ability to adjust for near vision. This makes near objects or writings appear blurred. This refractive error is typically first noticed in persons in their late 30s or early 40s.

Persons with this refractive error usually need to hold reading material at arm’s length to make letters clearer, and experience eye strain and headaches after reading.

Treatment for Refractive Errors

Anyone with problems seeing objects clearly or seeing objects at all are to visit their eye doctor immediately. Your doctor would access the eye and explain to you the type of eye problem you are having and also guide you on the best treatment option for you.

For refractive errors, they can be corrected with the use of corrective lens in spectacles or contact lens. The glasses or contact lenses helps to adjust the rays of light before it gets into the eye so that they fall on the retina at a single focus.

Laser-assisted surgery, such as LASIK, may also help by altering the cornea so that the rays of light fall on the retina.

So you see refractive errors are nothing to get worried about. Just see your eye care practitioner if you have any of the above symptoms and get relief for your eyes.

How to Find these Refractive Errors early

Every child should be checked for their visual acuity as soon as they are old enough to obey instructions and cooperate with an eye exam. A good number of children will not need to use glasses or any other correction of vision.

Also, after starting school, whenever a problem is suspected, whether visual or academic, maybe if the child is performing poorly at school, The children’s eyes should be screened. Short sightedness (myopia) is usually the commonest refractive error in little children who just started school. Hence, the children sitting at the back would not be able to see the board, and would not say so. You might see them either standing to see or walking up to the front to see. Most would not say anything and would continue to do poorly in school. However, this can be corrected with eyeglasses.

So when you see a young child doing poorly in school, try to take the child for eye examination to be sure it is not a visual problem.

I hope you were able to understand?

Feel free to ask any questions you may have below and i would do my best to get back to you as soon as i can.

Authors

  • Dr Jeme Adomi is a Clinical Optometrist with over 12 years working experience in the private and public eye care sector. She obtained her Doctor of Optometry from the University of Benin and a Masters in International Public Health from the University of Liverpool. She is also a Low Vision specialist and heads the Optics department of one of the major eye hospitals in Lagos state. She has a passion for public health education with an emphasis on eye care and wants to bring about a change in health care service delivery in Nigeria. You can follow Dr. Jeme Adomi on Twitter on: @JemeAdomi

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