This leads us on to today’s understanding of our eyes. Light is reflected off objects and projected onto our retina by the lens. The retina then detects this light and sends impulses along the optic nerve to our brain where the end result is decoded into what we know as vision.
Perfect vision (known as emmetropia) is achieved when the lens at the front of the eye projects light rays onto the back of the eye (the retina) in sharp focus, helping us to see images clearly. However, just as with a camera, if the lens is not adjusted properly these images can appear blurred. The extent of this blurring is known as refractive error, consisting of short sight, long sight, and astigmatism.
Other conditions include presbyopia (a condition related to age, where the eye beings to lose its ability to focus on near objects) and of course cataracts.