Human Eyes >> Normal eyes

we have knew that many people can not see the object clearly. They have problem with their eyes. but the other one have good vision. 

 Normal Eyes 

 Normal or perfect vision is the condition in which parallel rays of light are focused exactly on the retina without effort of accommodation. This is termed emmetropia. The optic system responsible for bending the rays of light is the cornea, aqueous, pupil, lens, and vitreous. All of these components which contribute to vision must be transparent, healthy, and functioning properly as a system, to achieve clear and quality vision. As the light strikes the photoreceptor cells of the retina, it transmits neuronal impulses along the optic nerve, via the visual pathway, to the brain for processing. 

 The process of when rays of light enter the eye from an object, pass through the optical system, and fall on the retina is called refraction. The total power from all the components involved in the refraction is measured in Dipoters. If the rays of light and image fall exactly on the retina, then there is no refractive error, and the power needed for correction is zero. 

 The eye is normal because the image is focused exactly on the retina without the effort of accommodation. what obout the someone who have refractive errors so they can not see clearly, 

Today you can undergo to LASIK