Understanding Your Vision

Understanding Your Vision

How Your Eyes Work

The eye is a sensory 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. The brain is then able to translate these impulses back to visual images.

How Our Eyes Work

All of this happens continuously and instantly to give us clear vision from near to far. 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. Even if we have always seen perfectly, over time, we are all likely to develop two conditions: presbyopia and cataracts. The images below provide additional information on refractive errors and these two conditions.

  • Presbyopia is the clinical term for near vision loss that starts affecting us in our 40s and 50s
  • Over time, the eye’s natural lens becomes too stiff to focus up close
  • Print and other nearby objects become blurry

  • Occurs when the eye’s normally transparent natural lens becomes cloudy
  • A “cloudy lens” prevents light from reaching the back of the eye causing images to lose their sharpness
  • Objects or text appear waxy, blurry or dull

Myopia (Nearsightedness)
  • 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

Hyperopia (Farsightedness)
  • 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