Common Defects of the Eye

Some common eye defects are:

  • Cataracts – Cloudy patches on the eye lens
  • Colour blindness – Difficulty distinguishing between different colours
  • Myopia – Cannot see far away objects clearly
  • Hyperopia – Nearby objects look blurry

Common Defects

Cataracts

A cataract is the clouding of the eye’s natural lens.

Cataracts get worse over time and they can only be treated effectively by replacing the cloudy lens with an artificial lens.

Myopia (short-sightedness)

Myopia, also known as short-sightedness, is a common defect where the image focuses in front of the retina. A person that is short-sighted can see near objects clearly, but distant objects are not focused properly.

There are two main causes of myopia:

  • The eyeball is too elongated, so it is oval-shaped instead of round – So the distance between the lens and the retina is too great
  • The cornea (protective outer layer) is too curved – Leading to the incorrect focusing of light that enters the eye, causing it to focus in front of the retina

Myopia can be corrected with a concave lens (glasses), which refracts the rays of light so that they focus on the retina.

Hyperopia (long-sightedness)

Hyperopia, also known as long-sightedness, is a common defect where the image focuses behind the retina. A person who is long-sighted can see distant objects clearly, but near objects are not focused properly.

There are two main causes of hyperopia:

  • The eyeball is too short from front to back – So the distance between the lens and the retina is too small
  • The cornea is not curved enough – Leading to the incorrect focusing of light that enters the eye, causing it to focus behind the retina

Hyperopia can be corrected with a convex lens (glasses), which refracts the rays of light so that they focus on the retina.

Treatments for myopia and hyperopia

Both myopia (short-sightedness) and hyperopia (long-sightedness) are typically treated with spectacle lenses (glasses). Newly available technologies offer treatments for both defects as alternatives to spectacle lenses. For example:

  • Hard and soft contact lenses – Invisible lenses that sit on the surface of the eye
  • Laser surgery – Change the shape of the cornea, which changes how it refracts light onto the retina. For myopia treatment, the cornea is slimmed down to reduce light refraction. In contrast, for hyperopia treatment, the shape of the cornea is altered to increase light refraction.
  • Lens replacement surgery – Replaces the eye’s lens with an artificial lens

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