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Why do nearsighted people need a prescription and a $300 pair of glasses, while farsighted people can buy their glasses at the dollar store?

Avery Davis Avery Davis May 19, 2023 · 2 mins read
Why do nearsighted people need a prescription and a $300 pair of glasses, while farsighted people can buy their glasses at the dollar store?
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The difference between nearsightedness and farsightedness is a common query among people who require corrective lenses. While we often see people who are farsighted wandering around with cheap reading glasses bought from a drugstore, those who are nearsighted don’t have such a luxury. They need to go through an extensive process to get a prescription and a more-expensive pair of glasses, and the question arises as to why this is the case.

Nearsightedness, medically known as myopia, is a common vision problem in which objects at a distance appear blurry. This is because the light rays entering the eye focus in the front section of the retina rather than on the retina’s surface. The opposite is farsightedness, also known as hyperopia, where objects appearing up close seem blurry, but objects farther away seem clear. This is because the light rays coming into the eye focus behind the retina rather than on it.

When it comes to correcting vision, the difference between the two lies in the type of lens needed. Nearsighted people need a concave lens, also known as a “minus” lens, whereas farsighted people require a convex lens, also known as a “plus” lens. Concave lenses allow the light to spread out before entering the eye, which compensates for the excess curvature of the cornea in the eyes of those who are nearsighted. Convex lenses, on the other hand, direct the light into the eye, which compensates for the flatter curve of the cornea in those who are farsighted.

At the root of the discrepancy in cost is the precise nature of the prescription. For nearsighted individuals, the amount of vision distortion can vary significantly, from -0.25 to -10.0 diopters. This forces the optometrist to take multiple detailed measurements to determine the correct lens power, which can take time and technical expertise. Additionally, the intricate process of grinding a concave lens involves taking off considerable thickness from the edge while maintaining a correct curvature throughout the entire lens.

Conversely, for farsighted individuals, the correction may be in the range of +0.25 to +6.0 diopters. This means that a simple convex lens can effectively fix their eyesight. This lens is relatively easy to manufacture; hence ready-made reading glasses are readily available in drugstores or the Internet at a much lower cost.

In conclusion, the primary factors that contribute to the higher cost of glasses for those with myopia include the need for precise measurements of the lens’s thickness and curvature, along with the technical expertise required for the manufacturing process. Furthermore, the higher range of correction required by those with nearsightedness results in more meticulous prescription requirements. Meanwhile, it is much easier to obtain suitable corrective lenses for those who are farsighted, leading to the lower-cost items available in stores.

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Avery Davis
Written by Avery Davis
Unleashing potential with passion and purpose.