The human eye
Our extraordinary organ of sight, second only to the brain in terms of complexity, composed of over 2 million working parts. The eye is the only part of our body able to function at 100% of its ability at any given time, day or night, without rest – that is when itʼs functioning properly.
How we see
Images we see are made up of light reflected from objects we look at. Light enters the eye through the cornea, which is curved, and is then bent or refracted to create an image on the retina, which in turn sends the image to the brain for interpretation.
Light entering the eye must be bent or refracted by the cornea in order for us to see. When bent or refracted light reaches the retina, photosensitive cells called rods and cones allow us to see images in colour, in detail, and in the dark.
It is our eye lenses that are responsible for focussing the image we see. Doing so, they activate muscles to change their shape, expanding to see distant images, contracting to see images nearby. In this way eye lenses are adjustable in much the same way that self adjusting glasses are adjustable.
What eyeglasses correct. Refractive error occurs when light entering the eye is not bent correctly by the cornea, resulting in a blurred or unfocussed image.
When distant objects, due to refractive error, appear blurry. Also called nearsightedness, myopia is inherited and is often discovered in childhood before progressing through the teenage years when the body is growing rapidly.
When objects close at hand, due to refractive error, appear blurry. Also called farsightedness, hyperopia is usually inherited. Children are often hyperopic though the condition may lessen as the child grows into adulthood.
Normal aging of the eye lens. At middle age, the lens hardens and becomes less flexible. This results in difficulty seeing at close range (reading, for example). It may also occur in combination with myopia, hyperopia or astigmatism.
A condition that usually occurs when the front surface of the eye, the cornea, has an irregular curvature. Normally the cornea is smooth and equally curved in all directions, which allows light to be equally focused in all directions. For those who suffer from astigmatism, the front surface of the cornea is curved more in one direction than another, a condition which often results in vision that is like to looking into a wavy mirror.