Common problems of the eye Flashcards
What is accommodation of the eye?
The process of changing the shape of the lens to focus on near or distant objects.
What happens to the eye when you need to focus on a distant object.
To focus on a distant object, the light rays only need refracting slightly to be focused on the retina. The ciliary muscles relax so the suspensory ligaments are pulled tight and the lens is pulled flat.
What happens to the eye when you need to focus on a close object.
To focus on clear object, light rays must be refracted strongly to be focused on the retina. The ciliary muscles contract so the suspensory ligaments loosen.
What are the two common defects of the eye?
Myopia and hyperopia. In both conditions light rays are not focused on the retina and the image is blurred.
What is Myopia (short sightedness)
Sees near objects in clear focus but distant objects light is focused in front of the retina so the images are out of focus and blurry.
Why does myopia happen?
Lens is too curved or a particularly long eyeball.
How is myopia treated?
Commonly treated by glasses with a concave lens.
What is hyperopia?
Can focus clearly on distant objects but close objects appear blurred.
What is the cause of hyperopia?
Lens is too flat and thin or a particularly short eyeball. As a result, les cannot refract light rays strongly enough.
How is hyperopia treated?
Commonly treated with glasses with a convex lens.
What are some new technologies to treat hyperopia and myopia?
- Contact lenses.
- Laser eye surgery
- Replacement lenses.
What is contact lenses?
Lenses that are placed on the surface of the eye. They can make life easier for playing sport and general activities. Some soft lenses last for over a month, but have to be removed and kept in a sterile solution overnight. Others are disposable - worn for a day and thrown away.
What is laser eye surgery?
Only available to adults once their eyes have stopped growing and their vision has become stable. Lasers are used to treat myopia by reducing the thickness of the cornea so it refracts light less strongly, focusing distant light to the retina. To treat hyperopia, lasers are used to change the curve of the cornea so it refracts light from close objects more effectively.
What are replacement lenses?
Add another lens inside the eye to correct the visual defect permanently. The risks include damage to the retina, cataracts developing if the natural lens remains in place and infections.
