Refractive error simply means the eye cannot properly bend (refract) light to focus it clearly on the retina.
In a normal eye, light passes through the cornea and lens and lands exactly on the retina, giving a sharp image.
When the shape of the eye or cornea is not perfect, the light focuses in front of or behind the retina — leading to blurry vision.
Types of Refractive Errors
- Myopia (Short-sightedness):
- You see near objects clearly, but distant objects look blurry.
- Caused when the eye is too long or the cornea is too curved.
- Light focuses in front of the retina.
- Hyperopia (Long-sightedness):
- You see distant objects better, but near objects appear blurry.
- Caused when the eye is too short or the cornea is not curved enough.
- Light focuses behind the retina.
- Astigmatism:
- Vision is blurry at all distances.
- Caused by an irregularly shaped cornea or lens (like a football instead of a perfect sphere).
- Light focuses at multiple points instead of one.
- Presbyopia (age-related):
- Happens around age 40+.
- Lens loses flexibility, making it hard to focus on near objects.
- This is why older adults need reading glasses.
Why People Need Glasses
Glasses simply correct the way light enters the eye.
- They add or subtract focusing power so that light reaches the retina properly.
- They compensate for the eye’s shape problems.
- They help you see clearly, reduce eye strain, and improve daily functioning.
Think of glasses as “external lenses” that help finish the job your eye cannot do perfectly on its own.