Eyes often need glasses because of a common problem called refractive error, which blurs vision. This condition affects how the eye focuses light onto the retina, leading to unclear sight at different distances.
The Primary Reason: Refractive Error
The fundamental reason people require glasses is the presence of refractive error. Instead of light bending correctly to focus a sharp image directly on the retina, it focuses either in front of or behind the retina. This misalignment is what causes vision to appear blurred or distorted. Glasses work by bending the light before it enters the eye, ensuring it focuses correctly on the retina and restoring clear vision.
There are several distinct types of refractive error, each affecting vision in a specific way. The provided reference specifically mentions four common types:
Types of Refractive Error
- Nearsightedness (Myopia): Difficulty seeing distant objects clearly, while close objects appear sharp. Light focuses in front of the retina.
- Farsightedness (Hyperopia): Difficulty seeing close objects clearly, while distant objects may appear sharp (though severe cases can blur all distances). Light focuses behind the retina.
- Astigmatism: Blurred vision at all distances due to an irregularly shaped cornea or lens, causing light to scatter and focus at multiple points.
- Presbyopia: An age-related condition, typically starting around age 40, where the eye's natural lens loses flexibility, making it difficult to focus on close objects.
Corrective lenses, such as those in glasses or contact lenses, are prescribed to compensate for these refractive errors, allowing light to focus correctly and provide clear vision.
