Refractive errors are vision related problems. These are the common reason for reduced level of eyesight (visual acuity).
What are refractive errors?
In refractive errors, the shape of the eye prevents light from focusing on the retina. The length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors.
There are four types of refractive error:
- Myopia (short sight).
- Hyperopia (long sight).
- Astigmatism (a refractive error due to an unevenly curved cornea).
Myopia (short sight).
This is also known by many as short or near sightedness. This result in distance objects appears blurry while close objects appear clearly. This is a common type of refractive error and usually corrected by spectacles or contact lenses. There is however special cases that needs laser eye surgery.
How does myopia develop?
Myopia develops when the images in the eyes that focus in front of the retina instead of on the retina, which results in blurred vision. This occurs when the eyeball becomes too long and prevents incoming light from focusing directly on the retina. It may also be caused by an abnormal shape of the cornea or lens.
What causes myopia?
Myopia can affect both children and adults. Myopia is often diagnosed in children between 8 and 12 years of age and may worsen during the teen years. Little change may occur between ages 20 to 40, but sometimes myopia may worsen with age. People with a positive family history of myopia may be more likely to get the condition.
What are the signs and symptoms of myopia?
Some of the signs and symptoms of myopia include:
- Difficulty seeing distant objects
- Difficulty seeing while driving at night
How is myopia diagnosed?
Regular comprehensive eye examinations are advised. It is during the eye examination that an Optometrist can diagnose and advise on what treatment is best suited for your eyes.
How is myopia corrected?
Myopia can be corrected with the use of spectacles, contact lenses, or surgery.
Spectacles are the simplest and safest way to correct myopia. Your Optometrist can prescribe lenses that will correct the problem and help you to see well.
Contact Lenses work by being in contact with the eye, thus providing a refractive surface for light rays entering the eye, providing a clearer and better focus. In many cases, contact lenses provide clearer vision, a wider field of vision, and greater comfort. They are a safe and effective option if fitted and used properly. However, contact lenses are not right for everyone. For more information visit your nearest SAOA Optometrist.
Hyperopia (long sight)
This is one form of refractive error, in which distant objects are usually seen clearly, but close ones do not come into proper focus.
How does Hyperopia develop?
Hyperopia occurs if your eyeball is too short or the cornea has too little curvature, so light entering your eye is not focused correctly, as a result near objects cannot be brought into sharp and clearly focused images. Hereditary factors often control the growth and development of the eye. However, environmental factors may also contribute to the development of farsightedness.
What causes Hyperopia?
People with hyperopia involuntarily exert extra effort to maintain clear distance vision and even greater effort to see clearly at close range. This extra effort can cause fatigue, tension and discomfort. If the crystalline lens of the eye cannot bring the object being viewed into focus, blurred vision occurs.
What are the signs and symptoms of Hyperopia?
Difficulty in concentrating and maintaining a clear focus on near objects,
- Eye strain
- Headaches after close work
- Burning eyes
- Irritability or nervousness after sustained concentration.
How is Hyperopia diagnosed?
Common vision screenings, often done in schools, are generally ineffective in detecting hyperopia. This is because these individuals can identify the letters on an eye chart with little difficulty. However a comprehensive optometric examination is preferred in diagnosing hyperopia.
How is Hyperopia corrected?
In mild cases of hyperopia, your eyes may be able to compensate without corrective lenses.
While in other cases, there is a need for the optometrist to prescribe spectacles or contact lenses to optically correct hyperopia. For more information visit your nearest SAOA Optometrist.
What is Presbyopia?
Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects.
Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented.
What are the signs and symptoms of Presbyopia?
Some signs of presbyopia include the
- Tendency to hold reading materials at arm's length,
- Blurred vision at normal reading distance and
- Eye fatigue along with headaches when doing close work.
- Reading glasses,
- Bifocals spectacle lenses
- Trifocals spectacle lenses
- Multifocal spectacle lenses
- Contact lenses.
How is presbyopia corrected?
A Comprehensive optometric examination will include testing for presbyopia.
To help you compensate for presbyopia, your SAOA optometrist may prescribe either of the following:
Presbyopia can complicate other common vision conditions like myopia, hyperopia and astigmatism, your optometrist will determine the specific lenses to allow you to see clearly and comfortably.
You may need to wear your glasses for close work like reading, but you may also find that wearing them all the time is more convenient and beneficial for your vision needs.
The effects of presbyopia continue to change the ability of the crystalline lens to focus properly, meaning that regular changes in your spectacles may be necessary to maintain clear and comfortable vision. For more information visit your nearest SAOA Optometrist.