Refractive error occurs when the light that enters the eye does not properly focus on the retina. When this occurs, objects appear blurry and out of focus. Glasses, contact lenses, and refractive surgery are all designed to alter the way light focuses on the retina in order to eliminate blurry vision. Refractive error is very common; nearsightedness, farsightedness, astigmatism, and presbyopia are all forms of refractive error. All types of refractive error can be identified and treated during a routine eye examination. Continue reading more about how refractive error affects vision, and how it can be remedied.
Myopia, more commonly referred to as nearsightedness, causes distance objects to appear blurry, while near objects are mostly clear. There are two main causes for myopia; it can occur if the eye is too long, causing light to focus in front of the retina, or if the refractive power of the cornea (the clear front surface of the eye) is too strong, causing light to bend and focus in front of the retina. In many cases of myopia, a combination of these two causes is present. To correct nearsightedness, glasses or contact lenses change how light is refracted as it enters the eye, pushing back the focus of light so it lands on the retina. Refractive surgeries, such as LASIK, can also correct for myopia by changing the refractive power of the cornea, and can completely eliminate the need for glasses or contact lenses. At PEP, we focus on myopia control, which uses different methods of preventing the progression of nearsightedness. Because high amounts of myopia can come with increased risks to ocular health, including a higher risk of a retinal detachment. Those with high myopia should have an annual eye examination to monitor ocular health.
Farsightedness is also called hyperopia. In this condition, the refractive power of the cornea is not strong enough, or the eye is too short, causing light to focus behind the retina. This results in images up-close appearing blurrier than objects far away. Some other symptoms of farsightedness can also include eyestrain, fatigue, and headaches associated with reading or near work. Hyperopia is less common than myopia, but many people tend to develop it later in life as the focusing system of the eye grows weaker and is unable to compensate for underlying levels of farsightedness. Contact lenses in glasses that correct hyperopia help move the focus of light forward, so that a clear retinal image is formed and up-close objects are easier to see.
While there are many common misconceptions surrounding astigmatism, it is simply a form of refractive error, just like nearsightedness or farsightedness. Astigmatism occurs when the refractive power of the cornea is uneven, meaning some parts of the cornea bend light different than other parts of the cornea. This most commonly results in distortions, both up-close and far away. Though astigmatism is commonly thought of as a dangerous or harmful condition, it can almost always be easily corrected with glasses or contact lenses. Regular astigmatism poses no threat to ocular health; in fact, most people have some degree of astigmatism.