What is normal vision?
In order to better understand how refractive errors affect our vision, it is important to understand how normal vision occurs. For persons with normal vision, the following sequence takes place:
Light enters the eye through the cornea, the clear, dome-shaped surface that covers the front of the eye.
From the cornea, the light passes through the pupil. The amount of light passing through is regulated by the iris, or the colored part of your eye.
From there, the light then hits the lens, the transparent structure inside the eye that focuses light rays onto the retina.
Next, it passes through the vitreous humor, the clear, jelly-like substance that fills the center of the eye and helps to keep the eye round in shape.
Finally, it reaches the retina, the light-sensitive nerve layer that lines the back of the eye, where the image appears inverted.
The optic nerve is then responsible for interpreting the impulses it receives into images.
What are refractive errors?
Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The following are the most common refractive errors, all of which affect vision and may require corrective lenses or surgery for correction or improvement: