DEFECTS OF VISION : DEFECTS OF VISION Myopia (short sightedness or near sightedness)
Hypermetropia (hyperopia or
long sightedness or far sightedness)
Presbyopia (old sight)
Normal Vision : Normal Vision Eyes
They are the visual sensory organs.
In humans, there is a pair of eyes that are directed forward and give binocular vision.
The eyes are situated in the eye sockets or orbits of the skull.
Slide 3 : Myopia is the medical term for near sightedness.
People with myopia see objects more clearly when they are close to the eye, while distant objects appear blurred or fuzzy.
Reading and close-up work may be clear,but distance vision is blurry. Myopia
Slide 4 : . Causes
Myopia usually develops in children or young teenagers. You are more likely to develop myopia if it runs in your family. The elongated eye ball in people who are short-sighted is the most frequent sight problem.
Slide 5 : Normal vision
When you look at something, light rays from the object pass into the eye through your cornea - the clear structure at the front of your eye - then through the lens towards the retina at the back of your eye. In a healthy eye the lens and cornea focus the light rays on a small area of your retina so that you can see the object clearly
Slide 6 : the condition in which parallel light rays are brought to a focus in front of the retina.
The condition is corrected by wearing spectacles or contact lenses with concave lenses and can now be treated surgically. Treatment Surgery
Laser refractive surgery
Recently laser surgery to correct myopia has become increasingly popular.
There are several different types of laser surgery. They involve using a laser to make small alterations to your cornea so that light rays are correctly focused onto your retina.
Hyperopia : Hyperopia
Slide 8 : Sight problems are very common, and many people are either long or short-sighted.
The percentage of people with long sightedness increases with age.
A study has shown that 13.2% of people who are between 20 and 25 years of age have hyperopia.
This increases to 17.4% for people who are between 40 and 45 years of age. It is thought that some cases of hyperopia may be inherited (run in families).
A gene has been identified that causes a very rare form of extreme hyperopia.
However, further research is needed into the possible genetic causes of the more common types of hyperopia. Hypermetropia
Slide 9 : Long-sightedness (hyperopia)In this case the eyeball is shortened, so that light beams only coincide behind the retina. Consequently, close objects are seen out of focus. This sight problem is often associated with headaches because the eye is overstrained.
Slide 10 : Long sightedness or hyperopia, occurs if a persons eyeball is too short or when
the cornea is too flat when compared to the normal eye. The light entering the
eye focuses behind the retina, instead of directly on it hence close objects look blurred.
Treatment : Treatment Hyperopia can be corrected using glasses that have a convex lens - a lens that curves outwards. These lenses ensure that light rays fall on to the retina, meaning you can focus accurately. Surgery
Surgical treatment for hyperopia involves increasing the curve of the cornea in order to increase its focusing power.
This is done by removing some tissue from the edge of the cornea.
The use of lasers to remove the tissue is increasingly preferred because the risk of damage or infection to the eye is much lower, than if surgical instruments are used.