Common refractive eye disorders
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- Last Updated on Sunday, 21 December 2014 22:05
World Braille Day on 4 January makes us aware that not everybody is born with perfect sight and vision. Some people see the objects around them as blurred and distorted images.
Having normal eyesight is like having an internal camera that takes thousands of snapshots while you are awake and busy with your daily tasks. It helps you to discern light and darkness, the colour and shape of objects by sending the appropriate signals to your brain. It even guides thousands of your movements.
Unfortunately, many people see the objects around them as blurred and distorted images.
It all starts with light
Your eyes function much like a camera. Light rays from your surroundings enter the eyes through the cornea, the clear “saucer” of tissue at the front of the eyes, travels through the lens where it is fine-tuned to focus on the retina at the back of your eyes and is then changed into electric impulses sent to the brain via the optic nerve. The brain unscrambles these impulse messages, interprets them and gives meaning to what you see. If your brain is unable to interpret these messages, you may have sight but not vision. On the other hand, if light is not focused correctly on the retina because of a fault in the shape of the eye or the cornea, you may have a refractive error and distorted view.
Common refractive eye disorders
Environmental and hereditary causes as well as ageing and even some diseases may cause refractive eye problems to occur. However, keep in mind that these conditions are eye disorders, not eye diseases. Eye diseases such as macular degeneration, trachoma, glaucoma (damage to the optic nerve) and the formation of cataracts are more serious conditions that may cause blindness.
Common refractive eye disorders include the following:
- Myopia (near-sightedness) that causes near objects to be in better focus while those further away are mostly out of focus or blurred. The cause: an unusually long (from back to front) eyeball that prevents light entering the eye from focusing on the correct spot on the retina. This condition may cause an involuntary effort to see better by squinting or narrowing the eyelids and may cause eye-strain, headaches, tension and discomfort.
- Hyperopia (far-sightedness) that may cause a person to see distant objects clearly but be unable to focus on objects that are close by. This happens when the eyeball is unusually short and, as in myopia, this may cause an involuntary special effort to try and see close-up, with similar results.
- Astigmatism has the disconcerting effect of making round objects look oval and distorted. It is caused by an irregularity in the shape of the cornea. If the cornea does not curve evenly, light rays can’t meet at a single, focus point on the retina, resulting in distorting images. Astigmatism is often associated with myopia and sometimes also with hyperopia.
- Presbyopia is often called middle-aged far-sightedness because it usually occurs after the age of forty. As with hyperopia the lens of the eye loses its ability to focus on nearby objects which makes reading a book, for example, so difficult.
Treatment options
Fortunately, most of the abovementioned common refractive disorders can be corrected with the use of spectacles, contact lenses or surgery. Surgery, especially laser surgery procedures to reshape the cornea and reduce or cure common vision disorders, have been highly refined over the years. However, there are also non-laser treatments available such as placing a phakic intraocular lens between the iris and the eye’s natural lens and corneal ring treatment, placing a tiny plastic ring inside the cornea to flatten its curvature, for those whose disorder can’t be corrected with laser surgery.
Contact lenses come in all shapes, sizes and even different colours; the choices are really mind-boggling. Spectacles have, over the years, become fashion accessories to be flaunted not hidden and are fitted with lenses that provide clear and continuous vision at all distances.
Do the check
It’s a good idea to have your eyes checked at least once a year, especially as you grow older. Also consider taking your children for an eye examination, especially before they start attending school. An experienced optometrist will quickly detect any refractive eye problems you may have and will be able to bring you up to date on all the corrective options available. If your vision problems can be solved by surgery, he or she will refer you to a specialist. Remember to also contact your medical fund to find out if and how much they will pay toward your expenses.
Sources
Common vision problems. Brochure obtained from Spec Savers
Feinbaum, C. Seeing the light on laser surgery. Brochure obtained from The Ophthalmological Association of South Africa
FAQ about Laser eye surgery. Retrieved from: http://www.hopkinsmedicine.org/wilmer/lasik/faqs.html#item22
Guide to common eye disorders. 2012. Froedtert & The Medical College of Wisconsin. Retrieved from: http://www.froedtert.com
Refractive errors of the eye: why some people do not see well. Brochure obtained from The South African Optometric Association
Revised by M van Os