Shortsightedness / Myopia
Shortsightedness, or myopia, is the most common refractive error of the eye, and it has become more prevalent in recent years.
In fact, a recent study by the National Eye Institute (NEI) shows the prevalence of myopia grew from 25 percent of the U.S. population (ages 12 to 54) in 1971-1972 to a whopping 41.6 percent in 1999-2004.
Though the exact cause for this increase in Shortsightedness is unknown, many optometrists feel it has something to do with eye fatigue from computer use and other extended near vision tasks, coupled with a genetic predisposition for myopia.
Myopia Symptoms and Signs
If you are shortsighted, you typically will have difficulty reading road signs and seeing distant objects clearly, but will be able to see well for close-up tasks such as reading and computer use.
Other signs and symptoms of myopia include squinting, eye strain and headaches. Feeling fatigued when driving or playing sports also can be a symptom of uncorrected shortsightedness.
If you experience these signs or symptoms while wearing your glasses or contact lenses, schedule a comprehensive eye examination with your optometrist to see if you need a stronger prescription.
What Causes Myopia?
Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.
Shortsightedness also can be caused by the cornea and/or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors.
Myopia typically begins in childhood and you may have a higher risk if your parents are shortsighted. In most cases, shortsightedness stabilises in early adulthood but sometimes it continues to progress with age.
Shortsightedness can be corrected with glasses, contact lenses or refractive surgery. Depending on the degree of your myopia, you may need to wear your glasses or contact lenses all the time or only when you need very clear distance vision, like when driving, seeing a whiteboard or watching a movie.
If you’re shortsighted, the first number (“sphere”) on your glasses prescription or contact lens prescription will be preceded by a minus sign (–). The higher the number, the more shortsighted you are.
“Most people with myopia would prefer not to become increasingly reliant on glasses or contact lenses for clear vision. It is through this desire that we as optometrists, have sought to understand the causes and key drivers of myopia, and hence position ourselves to seek ways of calming its progression.”
In most cases, shortsightedness is simply a minor inconvenience and poses little or no risk to the health of the eye. But sometimes myopia can be so progressive and severe it is considered a degenerative condition.
Degenerative myopia (also called malignant or pathological myopia) is a relatively rare condition that is believed to be hereditary and usually begins in early childhood. Degenerative myopia is a leading cause of legal blindness.
In malignant myopia, the elongation of the eyeball can occur rapidly, leading to a quick and severe progression of myopia and loss of vision. People with the condition have a significantly increased risk of retinal detachment and other degenerative changes in the back of the eye, including bleeding in the eye from abnormal blood vessel growth (neovascularization).
Degenerative myopia also may increase the risk of cataracts.
Extract from allaboutvision.com By Gretchyn Bailey; reviewed by Gary Heiting, OD