If you’re more visually inclined, this is a good video about how the eye takes light and enables us to see. It includes information about various parts of the retina and includes information about the function of the macula (it helps with periphrial vision).

Light rays from enter the eye through the cornea, the clear outer covering of the the eye. The cornea has a refractive power that bends the rays as they pass through an opening at the center of the iris known as the pupil. The iris is that colored part of the eye. It opens so as to make the pupil bigger and closes to make it smaller in order to regulate the amount of light rays that pass through it. Simply explained, the iris performs the same function as the shutter of a camera.

 
Human eye cross-sectional view grayscale
 

After passing through the iris, light rays pass through the eye’s lens which shorten and lengthen to further refract the rays and focus them properly on the retina. In a camera, the film has the same function as the eye’s retina. The retina is located at the back of the eye and has millions of tiny light sensitive nerve cells known as the cones and rods. Cones are found in an area called macula at the central part of the retina, where they are concentrated. They play a role of detecting colors and finer details so as to provide clear and sharp vision. On the other hand, rods are responsible for providing side vision. They are found at the outer part of the macula and they extend to the retina’s outer edge. Additionally, rods help the eye in detecting motion and better seeing at night or when light is dim. These cells (Rods and Cones) capture light rays, process them by converting into impulses and then send them through nerve fibers to the optic nerve where they are further sent to the brain where images are produced thus ending the process. This is how the eye works.

Every part of the eye plays a vital role in the whole process. Any defect in any part affects the process and results in eye defects that consequently weaken the eyesight thus calling for corrective measures. This takes us to the next part on how to correct bad eyesight using glasses.

How Glasses Help Correct Bad Eyesight.

Glasses help the eyes focus the light rays on the retina for better vision. In most cases, the common eye problems that affect many people are short sightedness and long sightedness. All these are caused by refractive errors that occur as a result of bad eyesight.

When you are short sighted, light rays are forced to focus early before reaching the right place(retina). Light rays are supposed to focus sharply on the retina and not any place in front or behind it. To correct short sightedness, glasses diverge the light rays so as to reduce the eye’s focusing power thus moving the focus point to the retina where it should be and not in front of it. Focus point belongs to the retina and when it moves to any place either forward or backward, it cause bad or weak eyesight.

For long sightedness, light rays do not form a focus point by the time they reach the retina due to the inadequate focusing power of the eye caused by the defect. This means that the focusing point is no longer on the retina and should be moved back to it so as to correct the defect. When your wear corrective glasses for long sightedness, light rays are converged thus increasing the eye’s focusing power which in turn moves forward the focus point to the retina. Glasses work like that.