Three Reasons Why You May Need Glasses
Here is some info dealing with some of the common eye troubles that may cause you to need prescription spectacles
Myopia - Also known as short sightedness, near sightedness
Nearsighted people can focus fine up close, but not at a distance. Distant objects seem blurred, whilst near objects are in focus.
DESCRIPTION
The eyeball is longer than usual, making the eye "too powerful." The image is focused at a point in front of the retina. The greater the degree of myopia, the shorter the point at which the Myopic can view clearly.
SOLUTION
Myopia can be corrected with the use of a concave lens system that is thinner in the center and thicker at the periphery. This type of lens system pushes the focus back onto the retina and restores good vision at any distance.
HYPEROPIA - Also known as long sightedness, far sightedness
Farsighted people see far better at a distance than close up. Even though distant objects seem properly focused, the accommodation required to focus on nearby objects causes eyestrain.
DESCRIPTION
The eye ball is shorter than normal which means the eye is not powerful enough. The eye is said to be "too short" and the image is focused behind the retina.
SOLUTION
Hyperopia is corrected with a convex lens which is thinner at the periphery and thick in the centre. This type of lens system brings the focus forward to the retina.
ASTIGMATISM
People with astigmatism have poor close and distant vision. They do not comprehend the contrasts between horizontal, vertical and diagonal lines in the same fashion as the rest of us.
Astigmatism is always accompanied by other visual impairment, such as Myopia, hyperopia and Presbyopia.
DESCRIPTION
Astigmatism is usually a result of an irregularly-shaped cornea that is slightly oval, instead of round, and oblong instead of spherical.
SOLUTION
Astigmatism can usually be corrected using a cylindrical lens whose curvature offsets the corneal irregularity.
