Vision problems are common, affecting many individuals. There is often confusion about “nearsightedness” and “farsightedness” and what types of glasses address these issues. This article clarifies which specific vision problem reading glasses are designed to correct.
What is Nearsightedness?
Nearsightedness, medically known as myopia, is a refractive error where distant objects appear blurry, while close-up vision remains clear. This occurs because light entering the eye focuses in front of the retina, the light-sensitive tissue at the back of the eye, instead of directly on it. This misfocus is due to the eyeball being too long from front to back, or the cornea, the clear front surface of the eye, having an overly steep curvature.
Symptoms of myopia include difficulty seeing distant objects, needing to squint, and experiencing eye strain or headaches. Myopia begins in school-age children, worsening between the ages of 8 and 15, and stabilizes between 20 and 40. This condition is corrected with concave lenses in eyeglasses or contact lenses, which refocus light onto the retina.
What is Farsightedness?
Farsightedness, also known as hyperopia, is a refractive error that causes nearby objects to appear blurry. This condition arises because the eye’s shape causes incoming light to focus behind the retina, rather than directly on it.
The anatomical causes of hyperopia involve an eyeball that is too short from front to back, or a cornea that is flatter than normal. Many children are born with mild farsightedness, which they often outgrow. Symptoms like eye strain or headaches, particularly after close work, can occur. Hyperopia is corrected using convex lenses in eyeglasses or contact lenses, which bring the light rays forward to focus precisely on the retina.
Why Reading Glasses Are Needed
Reading glasses correct presbyopia, an age-related vision condition distinct from general farsightedness (hyperopia). Presbyopia is a natural part of the aging process, characterized by a gradual loss of the eye’s ability to focus on close objects. This occurs because the crystalline lens inside the eye hardens and loses flexibility over time, making it difficult for the eye to change shape and adjust its focus for near vision.
As the lens becomes less pliable, the ciliary muscles, which are responsible for altering the lens’s shape, also weaken, further hindering the eye’s focusing mechanism. Symptoms include needing to hold reading material farther away, blurred vision at normal reading distances, and eye strain or headaches during close-up tasks. Presbyopia becomes noticeable in individuals in their early to mid-40s and continues to progress, stabilizing around age 65.
Reading glasses provide magnification to compensate for the eye’s diminished focusing power. Their lenses are convex, meaning they curve outward, which bends and converges light rays to focus directly on the retina, bringing close-up text and objects into clear view. The strength of reading glasses is measured in diopters (D), with higher diopter values indicating greater magnification to address more advanced cases of presbyopia.