Myopia is the medical term for near-sightedness, and occurs when light entering the eye focuses in front of the retina instead of directly on it. Individuals with myopia typically see objects that are close well, but have difficulty seeing objects that are far away. It is caused by a cornea that is steeper, or an eye that is longer, than a normal eye. Approximately 30% of people in the United States are near-sighted. Myopia typically starts to appear between ages 8-12, often progresses over childhood, and stabilizes by adulthood.
Hyperopia is the medical term for far-sightedness, and occurs when light entering the eye focuses behind the retina, instead of directly on it. Individuals with hyperopia usually have trouble seeing up close, but may also have difficulty seeing objects far away as well. It is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye. Because young people with mild to moderate hyperopia can often focus their eyes to see clearly, hyperopia is often undetected until later in life, when the eye begins to lose its ability to accommodate.
Astigmatism refers to the shape of the cornea of the eye. A cornea without astigmatism has a spherical shape, like a basketball. A cornea that has astigmatism has a more oval shape, similar to a football. Most astigmatic corneas have two curves – a steeper curve and a flatter curve. This curve causes light to focus on more than one point in the eye, resulting in blurred vision at distance and near. Astigmatism often occurs along with myopia or hyperopia.
Presbyopia is a term that is used to describe an eye in which the natural lens can no longer accommodate. Accommodation is the eye’s way of changing its focusing distance: the lens thickens during accommodation, thereby increasing its focusing power and its ability to see up close. As we age, the lens begins to lose some of its elasticity. This is a gradual process, although to many it appears to occur suddenly (typically around the age of 40). Most people first notice difficulty reading very fine print such as the phone book, a medicine bottle, or the stock market page. They may also have difficulty adjusting their focus from near to far. At first, holding reading material further away helps many patients, but eventually, correction is needed in the form of reading glasses, bifocals or contact lenses. Near-sighted individuals may simply be able to take their glasses off to read.
Options: There are four main options for correcting these refractive errors. These are glasses, contact lenses, refractive surgery or lens implantation. Feel free to discuss any or all of these options with your eye care professional to find out which one may be best for you.
Thank you to Dr. Ivan Jacobs, our guest blogger today, for sharing his insights and knowledge with us.