How Our Eyes Work
The eye is a tiny organ that measures about an inch long and weighs about 1/4 of an ounce. It is part of a complex system that translates light into images. Light enters our eye through the cornea and into the pupil. The pupil is the black hole in the middle of the iris, the colored part of the eye. Behind the iris is the natural lens. It focuses the light onto the retina, the inside layer of the eye. The retina contains cells that are sensitive to light. The image is then converted into electrical impulses that are sent through the optic nerve at the back of the eye to the brain.
All of this happens continuously and instantly to give us clear vision from near to far distances. But, our eyes don't always work perfectly. Their exact size and shape affect how well they focus light. These differences can cause some of us to have refractive errors such as myopia, hyperopia or astigmatism. In addition, over time, we all lose our ability to focus on near objects. This is a refractive condition known as presbyopia.
- Presbyopia is the clinical term for near vision loss that starts affecting us in our 40's and 50's
- Over time, the eye’s natural lens becomes too stiff to focus up close
- Print and other nearby objects become blurry
- Ability to clearly see near objects, but distant objects are blurry
- Occurs when the cornea is too rounded or steep, or the eyeball is too long
- The eye’s refractive power is too strong
- Ability to clearly see distant objects, but nearby objects can be blurry
- Occurs when the cornea is too flat or the eye is too short
- The eye’s refractive power is too weak
- Light coming into the eye is focused inconsistently
- All objects are stretched or distorted
- Occurs when the cornea has an irregular oval shape
- Can occur simultaneously with nearsightedness or farsightedness